Just to extend a bit on the previous advice: for any software with a database at its core (guayadeque, shotwell, etc...) is good practice to back it up as they do get corrupted, or they can be lost some how.
Incidentally I use Lightroom for my photography (I know, I know...). Its database functionality is very sophisticated and it has got corrupted more times I can remember. But it more or less forces you to back it up regularly so when this happens you can easily recover from disaster.
I think this is a bit of a weak point in guayadeque: I believe the software should take better care of the database (by backing it up). It is a common thing for people to have issues with databases.
Of course the more guayadeque permits to store metadata into the files themselves the less relevant the problem is.