Our assembly was saved in 2010 & contained some toolbox bolts that were mated correctly

Now that Im opening them in 2011 the mates for these toolbox parts are all suppressed? Is there a reason for this?

Ive also noticed in the past when opening previously saved assemblies containing toolbox parts that sometimes they have errors flagged up with mates, but if I close the assembly & re-open then they're fine, which is really frustrating!

We're now thinking of creating our own parts library of fixings  that will make us less dependant on the toolbox - is this a good idea?