If the software has a dongle or offline serial code then you should be OK, just save a copy of the installer.
If the software uses online activation / phone activation etc or they supply you with a license file that is locked to your machine i.e. you give them an "activation code" that shows up on the screen in the software somewhere, they generate a key and send it to you, as soon as that company ceases to trade, depends if it is bought out, licenses will change and possible not be usable.
Prime example is Eagle, if you have a license for v7 you can still install and use v7, from v8 onwards the license model changed to subscription and now essentially doesn't exist as its own product as is tied in with Fusion 360.