hello, nightly is an early development version that receives daily updates (or nightly as its name is already suggesting). in case you want to use a regular firefox version, please use the release version (updated each six weeks) or the beta version (updated roughly every 5 days): https://www.mozilla.org/firefox/channel/#firefox

Nighty is one of the four main development channels. Nightly, Aurora, Beta and Release. The Nightly and Aurora channels usually get checkins every day so therefore they get a update each of those days, with the occasional respin the same day. Sometimes there can be regressions and result in a unusable build that day until the problem checkin(s) is either fixed or backed out.

Unless you want to be a Tester, you probably should just stick with Release or Beta (currently at 32.0b8) at most.