I wouldn't worry too much about stretching it. My upper arms are 16", and the chevy bowtie tattoo I got years ago barely looks any different. My arms were about 14" when I got it. Only I can see the difference, to anyone else it looks the same. Unless you plan to be extremely huge. And don't give me any crap about the bowtie thing. I'm gettin' the turbo 6 on the other arm soon.
Inks have come a long way, and the guy who does my tatoos has some very old ones that still look awesome with no touch up work. I think the healing period is the most important, since any damage could cause a blemish later on. I got hit with a 10' stick of 3" pipe while mine was scabbed over, and it peeled the scab. I have a dull spot there now that will have to be touched in. BTW, if your guy can do it, get something chrome. Its sweet! My bowtie is chrome, and it looks cool. I think tattoos are becoming more and more socially acceptable, as you see more "upper class" people with them. I was shocked by how many older professional clientele my tat artist had. I want sleeves, but I am worried about making impressions on new people, and since my job requires me to meet new people every day, I don't want to offend or mislead someone. But I wouldn't hesitate to get another one, where its not visible with a shirt on.