Short answer Yes.

Just be aware there is a huge list of security vulnerabilities that have been fixed since 31 came out. While it is your choice, I would like to be sure it is an informed choice. See the list here https://www.mozilla.org/en-US/security/known-vulnerabilities/thunderbird/

hi Matt, Thank you for response. We have selected the "custom" install and installer smoothly found existing Thunderbird installation and replaced it.

Thank you for pointing out that we need to be aware of vulnerabilities. I think we will migrate to newer version of Thunderbird but need to check their system requirements and whether they would eg. allow to easily "move" the profiles to new computer once we change computers. We heavily use filtering etc. so we do not want to re-create them from scratch etc. Thank you, Grzegorz

Thunderbird 91 (until about 10 minutes before it was released has a profile import export tool. It was pulled at the last minute because the process was limited to 2gb profile and that left to many out in the cold, but it is still hoped to see it is V91 sometime this year. Beyond that there has been so little change in Thunderbird profiles in the past decade that really an update to the current version will have issues with addons, but that is about all. Other profile changes update on the fly the first time the new version of the program is run.

System requirements are really very modest.

Windows Operating Systems (32-bit and 64-bit)

   Windows 7
   Windows 8
   Windows 10

Recommended Hardware

   Pentium 4 or newer processor that supports SSE2
   1 GB RAM / 2 GB of RAM for the 64-bit version
   200 MB hard drive space

See https://www.thunderbird.net/en-US/thunderbird/91.0.1/system-requirements/ for other operating systems.

Thanks a lot for all clarifications. Best, Grzegorz