I have had periods when I have been aware of ectopic beats, usually accompanied by a vague thump in the chest. I've had a 72 hour holter, which didn't pick up any extrasystoles! I've also had a few episodes of tachicardia (not very nice). I still hold my Class 2 medical, although I lost it 11 years ago for 3 months when I was having quite frequent periods with ectopic beats (about 5 per hour, sometimes mutiple ones). However, I've also had long periods of time with virtually no ectopics. During the time when my medical was suspended I had all the usual tests including exercise treadmill and echocardiogram, but the tests revealed nothing abnormal. My annual ECG for the medical is always perfectly normal.
I exercise quite a lot (hill-walking mainly), am underweight for my age (59) and height and for 2 years have had slightly raised systolic BP for which I take a low dose of amlodipine.
I'm afraid a beer or two definitely makes the extra beats more likely, but a cup of strong coffee doesn't seem to bring them on. There's definitely a stress related factor, but it seems to have a delayed effect, sometimes weeks afterwards.
I'm told this condition is very common, especially in the over-50's. My experience of dealing with AME's is that (at least in the UK) they want to keep you flying, and will do all they can to help you keep your licence.
Of course, especially with ticker-related problems, everyone's physiology is slightly different so I'm not trying to impart any advice here, just reporting my own experience of the problem.