I get about 2 1/2 seasons out of a pair. averaging about 45-50 days a season. Somewhere after 100 days is where I expect the clock to really start ticking on the life span of the boot.
You should probably mark your days on a calendar to see how many you are putting in. When I say 100 days I do mean 100 full days. Not going for a few hours, but all day beat on your gear riding.
When your boots are all packed out, mushy, and your feet hurt as soon as you put your binders on, it's time for a new pair.