Seadweller help

[mamas]

Guys, i have owned my SD since april 2005 and has been consistently -1 sec / day for around a year or so, and over the past few months has been around +1 sec / day.
i set my watch around a week or so ago, and when i checked timing yesterday, it was around +40 seconds fast! I obvioulsy thought i had made a mistake, so reset yesterday and it was around +6 seconds fast over 24 hrs and today will be around that too!. i do understand that it is still within cosc standards but it seems very odd that it is suddenly gaining time after being so stable for so long!!
3 questions:
1) what is going on?? no history of trauma from my end adn hasnt been near any magnets!! should i send it to be checked out?
2) how long is rolex warranty.. is it 1 year or 2? ..
3) How much should i let it go fast by before sending it in for checking out?
thanks