For example, as my first weapon I have a wand which adds some skill bonuses to my summoning tree. If I summon skeletons and then switch to a different weapon, would my already summoned minions' stats (hp, damage etc.) change to match my current summoning skill values?
Sorry for my english if I put it not clear enough.
And the second question. Summoned minions tend to dissapear randomly, especially if they are in large numbers and you are moving fast. Do you know what exactly does make them disspear, so maybe I could avoid it and reduce my chances of losing a good Iron Golem. Any tips would be appreciated.
As zeph said, minions will always stay at the level you summoned them.
Revives tend to disappear in those circumstances, skellies will luckily teleport to your position once they lag too far behind. That (and the fact that they're dumb as rocks) is the reason why I've always avoided revives completely. As for IG, I'm pretty sure he'll teleport to your position, but I know they tend to poof sometimes. There's really nothing you can do to stop this other than using teleport or moving through areas slowly while making sure he keeps up with you.
I have used townportal cathering myself and it's fast and cheap. Yep, it's not very professional or cool way but for some reason I dont like losing skeles by swapping weapons. I also keep tiara with telecharges in inventory but it's not fast or best way to gather minions. Mainly I use tele in maggot lair or other nasty places.
If I run fast a long time i tend to lose some skeles and mages also, not only revives.
Hmm, if I only could afford enigma. It's maybe one of the most powerfull item for summoner?