I would definitely upgrade to FTM2012. There are dozens of updates and changes from FTM2011 - even not counting the sync feature (which I don't use either).
What some users do, including me, is to identify our file names with the version that file is associated with. For example, before I upgraded to FTM2012, my file was xxx2011.ftm and was in:
FTM2011 Data Files
....xxx2011media (folder) - with contents.
I then created new folders:
FTM2012 Data Files
.... xxx2012media (folder with contents)
I copied xxx2011.ftm to the 2012 file and changed the name in Windows explorer and also copied all of the contents of the media folder.
I then brought up xxx2012.ftm in FTM2011 and made sure I had everything - the number of individuals agreed, sources, images, etc. I also went into media and used the FTM edit to find unlinked images and told FTM to find any it found.
I then exited FTM2011 and installed FTM2012 and told it to open the file xxx2012.ftm. That file will be changed by FTM2012 and cannot be read by earlier versions.
I have the data files associated with each version of FTM for the past 10 years on my hard disk.