Multiple lily versions on ubuntu

[Simon Albrecht]

Hello,

I recently exchanged Windows for Lubuntu on my computer. Lilypond 2.18.0 
is already installed and I want to add 2.19.3, but when I run the 
installing file, it requires that I uninstall the "old" versions before 
installing the new one. However, I want to have both at hand, as it 
seems to me is common use (correct me if I'm mistaken).
So first, is it a good idea just to rename the existing directory into 
/lilypond_2.18.0 and thus escape the problem? And second, wouldn't it be 
handy to provide for multiple lily versions installed at the same time 
or at least make this an easily available option in the installation 
process (like --keepold for example)?
Best regards,

Simon