I don't use MongoDB, but I imagine the answer to that question for most people is: No, because I already have an existing product in production with actual customers, and I can't afford to upgrade to the latest version.
With a replica set you should be able to do the update with zero or little downtime with some planning. Of course you'll have to look and watch for breaking changes if you running a really old
version.
It's not just the downtime. It's the actual work involved in running all your regressions to ensure backward compatability. ie. do all your existing queries still work? do all your current backup processes still work? did that arcane config variable you rely on change its stinking name?
I was going to respond with “well, any database that can’t guarantee that kind of backwards compatibility shouldn’t be taken seriously,” but then I realized we are talking about MongoDB and I found myself giggling.
I don't use MongoDB, but I imagine the answer to that question for most people is: No, because I already have an existing product in production with actual customers, and I can't afford to upgrade to the latest version.