On descaling, and the thing that actually determines everything: what water you have been putting in it.
In a hard water area, two years of daily use with untreated tap water means there will be significant scale. In a soft area with filtered water, possibly very little.
So find out your water hardness first: your supplier publishes it, and cheap test strips exist. That tells you both how urgent this is and how often you will need to do it in future, which is the number nobody can give you generically.
On doing it:
Use a descaler intended for coffee machines, and follow your machine's own procedure. Some machines must not be descaled with certain acids, and some have components that are damaged by it - this is why the instructions differ and why the manufacturer's version is the one to follow.
Expect the first one after two years to be unpleasant, and possibly to need two passes.
Then prevent it. Filtered or softened water for the machine from now on. This is far more effective than descaling more often, and in a hard area it is the difference between a machine that lasts a decade and one that lasts four years.
If the machine has been struggling to reach temperature or the flow has dropped, that is scale talking and it is already well advanced.