You don't have to guess, you can measure. Have it pumped once now to get a known starting point, then check the sludge depth yourself annually with a stick and a rag, or with a cheap sludge judge tool: you're looking at the depth of solids at the bottom and scum at the top, and the rule of thumb is pump when solids reach about a third of the tank depth or when the scum layer is within a few inches of the outlet baffle. For two adults on 1000 gallons with no disposal, four to five years is a very common real answer, but measuring costs you an hour a year and takes the argument away entirely.
Just be sensible about it, don't lean over an open tank, don't go in one ever, and put the lid back properly. Otherwise it's a five minute job.
Two dentist visits, a boiler service and a laptop in the first six months, all of which I'd been putting off for years. That's most of the gap right there.
The heating one is real, our gas bill is up nearly 40% and I'd never connected it to being in the house all day.
Hot only means the water heater, essentially always. What's happening is sulphate reducing bacteria living in the tank reacting with the magnesium anode rod and producing hydrogen sulphide, which is your rotten egg smell. Two-part fix that has worked on three houses for me: drain and flush the tank, then swap the magnesium anode rod for an aluminium-zinc one. Some people go to a powered anode instead, which costs more and lasts far longer. Do not just remove the anode and leave it out, the tank will rust through in a couple of years.
Handy person, but the rod is often seized in there and you'll want a breaker bar and a six point socket, plus enough headroom above the tank to pull a metre-long rod out. Segmented rods exist for tight spaces.
The rule takes care of it. The first year I checked balances weekly and felt terrible, now I look four times a year and I feel fine. Same portfolio.
Mine is boring: 60/40, withdraw quarterly from whichever side is above its target, no cash buffer beyond three months. It has worked for six years. The bucket strategies aren't wrong but a lot of them are the same thing with more moving parts and more chances for me to fiddle.
Bigger is generally better, longer run times and fewer starts. The only limits are space and the fittings. Going to a 40 or 44 gallon is a common upgrade and your pump will thank you.
That's a waterlogged tank, and yes, it's hard on the pump, so I wouldn't leave it for weeks. The bladder has either failed or the air charge has leaked out, and a tank that sounds solid most of the way up is the classic sign. Test it properly: turn off the pump breaker, open a tap to drain the pressure to zero, then check the air valve on top of the tank with a tyre gauge. It should read 2 psi below your cut-in, so 28 for a 30/50. If air comes out fine but reads low, recharge it and see if it holds. If water squirts out of that valve, the bladder is torn and the tank needs replacing.
7% real is an optimistic input to build a life plan on. I ran mine at 4.5% real and treated anything above that as a bonus, which meant I coasted about two years later than I could have but I've never had this particular conversation with myself. If you rerun your model at 4.5 and the answer is still 'mostly fine, retire at 62 instead of 60', that's probably your real answer.
Then the shock did its job and you've got a straightforward iron problem left. Get the test redone for both ferrous and ferric iron before you buy anything, since that changes which filter suits.
Shocking treats bacteria, not iron, so at 1.8 ppm dissolved iron you're going to get that staining back every time regardless of how well you chlorinate. What shocking does help with is iron bacteria, which is a different thing that looks like orange slime rather than staining, and if you had both then the slime went and the iron stayed. You need removal, not disinfection: at that level and that pH, an air injection iron filter or a manganese greensand system is the usual answer, and a softener alone will clog eventually.
I'd keep the 3.9% and invest, but with one condition: you have to actually invest it, every month, without touching it. Most people who make the mathematical argument end up with a mortgage and a slightly bigger car. If you know you'll keep the discipline for two years, the numbers are on your side. If you don't, the mortgage is a forced savings plan with a decent return.
The honest difference is service intervals and how much iron gets through. A cartridge system at 2.1 ppm and 150 gallons a day will need new cartridges every three to six weeks, which is both a real cost and a chore you will resent by August. The two-stage system handles the iron in a backwashing filter so the softener only has to deal with hardness, which is what softeners are actually good at. If 3,400 is out of reach, the middle path I'd take at 1,500 is a single air injection iron filter now and live with 14 grains of hardness until you can add a softener, rather than trying to make one softener do both jobs.
Important one. Routing backwash to a dry well or a separate drain rather than the septic is common practice and worth pricing up front, not after.
Third person recommending the fake paycheck. It's the highest ratio of benefit to effort of anything I did in year one.