I had an opponent that played all the above tricks on me, before going on vacation, facing mate in one in our game.
However, I had a "Gambit variation" at my disposal:
1. I wrote an item in my blog (now deleted) telling my opponents I was going away for a while.
2 I then set my positions to "vacation".
3 Logged off.
4. Logged back on one hour later... and guess what? Yep! he'd played his final move.
**Addenda** He seemed a little annoyed that I refused his rematch challenge and sent him a lesson in etiquette at the same time. Oh! happy day!
I had a LONG vacation with my parents last year. (TWO WHOLE WEEKS) And limiting vacation would have made me lose games if I was on the site then.