hello mam/sir . To know what's new in update check this out! https://blog.mozilla.org/futurereleases/

The MozillaZine Builds forum has a recap of which Bugs are fixed in each new pre-release version. A new thread is started each day, and covers Nightly, Aurora, Beta, and sometimes covers special builds, like the current Holly (Nightly without the Australis interface).

Those thread are entitled as such. The date changes everyday with each new thread.
The Official Win32 20140201 builds are out
http://forums.mozillazine.org/viewtopic.php?f=23&t=2797253

Quite honestly, you should consider using the 32-bit release version rather than the "cutting edge" Night 64-bit version, which isn't currently being developed or supported.

Both the Nightly (29.0a1) and Aurora (28.0a2) channels get checkins pretty much everyday so therefore they get a update each of those days. Sometimes they even get a respin update the same day if there was a issue(s) that got fixed right away and if you miss this respin the next update will be a full one instead of partial.

Nightly builds are not meant for regular users but more for testers/devs and those who understand at least the basics of separate installs and separate Profiles for each.

The Nightly channel can get a lot of code check-ins: over 1200 during the past 7 days.

• http://hg.mozilla.org/mozilla-central/pushloghtml?startdate=7+days+ago&enddate=now

You can consider to use the Aurora update channel (each day) or Beta update channel (twice a week) to have a more stable version.

• http://www.mozilla.org/en-US/firefox/channel/