Battle difficulty when upgrading items
 

I just had the feeling that the longer the harder the battles will be to upgrade an item. Is this true, does the number of enemies scale somehow with the level of my character?

No they dont scale with ur level, but they are often set between different lvls / game, the can bet set at lvl30 - 34 and pop up in ur game at one of those lvls.

So u have a sort of diversity in ur games, same as with the creatures, its set at a bit of diversity, so its not same troops everytime u meet them.

ecania