The best way to get the most life out of your chain is to keep it clean, not the easiest thing to do in the winter.
The easiest way to clean the chain is to take it off the bike, the cassette and chainrings are also more accessible.
Christmas is coming, if you've been good boys and girls perhaps Father Christmas will put a quicklink removal tool in your stocking to help with this job.
Agreed in principle! But personally, I would never want to split/rejoin a chain once it's on, its just asking for trouble, and things like that have a habit of failing when you're coldest and furthest from home. I try to keep as clean as possible and re-lube when on the bike, and replace the chain every few months anyway. Your cassette practically lasts forever if you don't run the chain past it's best.