Personally I do about 3-5 a year, plus 1 or 2 half marathons, a 10 miler, and several 10k, and 15ks.  2 is not too much of you train and recover properly.  I do know that there are people out there that do way more than I and are fine, again, properly trained.  Good luck!

-Anthony

I'll do anywhere from 4-7 tri's per year depending on my goals for the year.  If I'm following the Xterra circuit or if I have a major race in the fall I tend to do more.  This year I have 7 planned, 1-2 per month with 3 tri's in 3 weeks during one stretch.  I really try to support the local Tri's when possible.  You can do more sprints without risk of injury compared to Olympics/Half- or Full-Iron distances.

I determine what races will be an "A" race where I taper and go for it, "B" races where I do a modified taper (take the 2 days easy before the race) and still go hard and "C" races where I just consider them part of the training week and just a high intensity swim-bike-run brick.

There's nothing like racing to really get your heart rate beyond the lactate threshold zone.  I'll also do some 5 and 10K's with an occasional Adventure Race or bike race.  Again you don't have to go all out but consider them training days or "play".

I plan my training upon my "A" races and distance.  I have been mainly focusing on Olympic distances recently so I stick with that training plan from January until September/October.  I consider the Sprint Tri's a test of my training plan and effort as well as a high intensity workout.

If you have never done a Tri before, first focus on the plan that will allow you to complete the race.  After you complete your race, look at the volume of training that the Sprint plan has versus the Olympic plan.  If the 2 plans have a similar volume then just jump right into the Olympic plan. 

If you have been training consistently before the start of your 4-week Sprint plan and your volume of training is similar to the Olympic plan, go ahead start the Olympic plan at 12 weeks out from the Olympic.  3 days before your Sprint Tri do a modified taper cutting all your training volume in half for the next 2 days and just do a warm-up of all 3 or take the day off the day before the race.

Look at your workout plan for your 2nd Sprint tri and how that fits in.  You can do it with a modified taper or just do it as it falls on your schedule.  Just make sure you don't have a hard run set in the 3 days before the race.  Some plans go by a 3-week hard/1-week recovery (cut volume in half) schedule.  If your lucky, your other races may fall at the end of a week that has been easy.