Browsing the darknet with an out of date tor browser? During the update from 5.04 to 5.05 it auto updated to 5.05 while I was browsing on the markets. I dont remember seeing the thing on Tor's home screen telling me I needed to update but how big of a screw up would it be if it was a required security upgrade?
It's probably not that big of a deal unless you're doing something illegal (or unless you're a vendor), but I'd still take the 30 seconds to update it.
I can't tell you how long I went without upgrading Tails, and that was over a few months of ordering. Very stupid OPSEC mistake, but if you're just accessing reddit you could probably use versions from months ago without any issues.