Aside from the health benefits I find it just makes things easier for practical reasons a lot of the time. My DC3 is 11 months and still exclusively BF (and on solids obviously). We have been on holiday recently and it was easier at the airport as I didn't have to pack the milk/get it through customs etc, or worry about buying formula on holiday.
I will carry on past a year and see how long she wants to BF after that, but in a month she will be able to have cows milk so if I have to go out and she wants a drink she can just have a beaker of that and a BF when I get back.
I am a SAHM so obviously it is easier for me to exc bf than if I was back at work, but if I was working I think I would have just carried on bf when around her and given her formula or EBM when away (depending on if it had been practical to express at work or not).
Like others have said it is nice just to have the excuse for a cuddle and I quite like that fact that no one else can do this - so when family are around no one has been able to persuade me to let them give her a bottle.
I sympathise with the mastitis thing though. I have had that a couple of times with DC3 (though never with DCs 1 and 2 who I also fed for over a year each). Haven't had it for a while now though and I think these problems do usually go away after a few months.
I would advise to get a couple of very supportive and nice feeding bras (if you haven't already). I have friends who can't wait to get out of their unflattering feeding bras and back into their normal ones, but because I don't have a bra that makes me feel frumpy then that doesn't bother me. I justify the extra expense by thinking of the money I have saved on formula and feeding equipment!