I have spent decades in the woods and almost never see snakes — is that normal or am I just not looking?

The behavioural half is worth stating clearly because it is reassuring rather than alarming: they are avoiding you deliberately and they are good at it.

A snake gains nothing from an encounter with something your size. Venom is metabolically expensive and produced for prey, and using it on a creature far too large to eat is pure loss. Every defensive behaviour — retreating, freezing, warning displays, dry bites — is arranged to avoid that expense.

Which is also the practical advice. Most bites occur when somebody steps directly on one, reaches blindly into a place they cannot see, or tries to handle or kill it. Walking normally, looking where you place hands and feet, and stepping onto logs rather than over them removes nearly all of the realistic risk.

So your decades of not seeing them is not luck. It is the system working.

You have walked past a great many of them, and this is close to universal — it is one of the first things you notice when you start looking deliberately.

Three things are working against you:

They detect you first. Snakes are exquisitely sensitive to ground vibration. A person walking is an enormous signal, and the response of nearly every species is to leave or to freeze before you are anywhere near. You are being avoided, continuously, by animals you never register.

They are built not to be seen. Camouflage in snakes is extraordinary, and it is specifically tuned to the substrate they live on — leaf litter, bark, gravel. A motionless snake on the right background is genuinely invisible at two metres, and freezing is the default response of many ambush species.

They are mostly not where you are looking. Under things, in things, and largely active at times of day when you are not there.

Surveys that use proper methods — cover boards, transects, trained observers — routinely find densities that astonish people who have walked the same ground for years.

If you want to start seeing them, the conditions matter far more than the effort:

• Temperature. Snakes are most visible when they need to warm up and least visible when it is too hot or too cold. Mild mornings after a cool night, and the shoulder seasons, are the productive times.
• Edges. Where two habitats meet — forest and clearing, bank and water, rock and grass. Far more productive than the middle of anything.
• Look at flat objects. Sheets of bark, boards, corrugated metal, flat rocks. Lifting these carefully, towards yourself so the object is between you and whatever is under it, is how surveys actually find them.
• Slow down and stop. Movement is what you detect and stillness is what they do. Standing still for two minutes reveals more than an hour of walking.

Do that for a couple of mornings and your lifetime count will change substantially, which is itself the answer to your question.

One detail that surprises people: you probably also have a strong regional effect.

Snake abundance varies enormously by geography, habitat quality and how much the surrounding land has been developed. Two forests that look identical can differ by an order of magnitude, depending on what the surrounding landscape does for their prey and their overwintering sites.

So part of the answer may genuinely be that where you walk supports fewer than you would assume — but the observation bias above is doing most of the work in almost every case I have looked into.