I was 27 when I was diagnosed with an 18mm ASD which was a HUGE SURPRISE since I had been a pretty serious athlete for my entire life ( i'm 33 now). Anyway, I didn't have a choice about whether to close it or not because of the size and because of the size that my heart enlarged to. My doctor and I discussed options including the implatzer (sp?) device for closing it. I actually chose open heart surgery because I didn't feel like the device had been around long enough for me to feel comfortable making that decision. I think in europe they had only been using it for about 10 years and here perhaps 5? The data is pretty solid-- the data they have. There was very little risk involved in the device but what happens in 20, 30, 40 years? They just don't have that data yet. My rational for having open heart surgery was just that they have been doing it since the 1960s and that if they went in and manually sewed the thing shut, I would never have to think about it ever again. With the device, I would always be wondering if it would be ok or not. That is mostly about me and my personality as a worry wart. At the end of the day, if you are going to spend the rest of your life worrying and being concerned and psyching yourself out, just get it fixed. If you are not that type of person, it sounds like they could just monitor it closely and fix it when needed.
Anyway, that's my 2 cents.