My Limits?

Last week I had a rest week with regards to training, but the previous weeks involved a weekly hill climbing session on Torrey Pines grade.  These workouts consisted of progressively more difficult climbs, as measured in watts.  For example one week I was supposed to do the first climb at 230 Watts, then next one at 240, then 250, 260, and finally 270.  I worked hard to meet those numbers, 270 watts wasn't easy - my legs were burning.  But, I hit the numbers and so the next week the targets shifted up to 240, 250, 260, 270, and 280.  Once again I didn't think I could do 280 after having done the first part of the workout, but I did.  So the following week the goalposts shifted again to 250 up to 290 watts.  I was sure I couldn't do 280 watts and then do 290 immediately after, but once again I did it.  This time it didn't even feel like I was doing something impossible - it was just something that needed doing.  I'm sure next week coach will have 300 watts on this workout.  Holy hell I can't imagine finishing my workout with 10 minute climbs of 280, 290, 300 watts!  Crazy.
Anyway, it occurred to me that eventually I will hit my limit.  At some point (maybe at 300 watts!) I just won't be able to do what is being asked - it just won't be in me.  So what are my limits?  It's not something I'm comfortable even thinking about.
On a bike I feel like I can do anything I set my mind to.  I've yet to set a goal and not hit it, though admittedly there are some things I've pushed to the back of my mind, for now :)  In other athletic endeavors my limits are much more obvious to me.  I can't run a 6:00 minute mile, or a 100 mile ultra marathon.  I can't swim the English channel, nor can I do a 1 minute 100 meter.  But it doesn't matter to me that I cannot do those things - there's plenty of improvement to make and goals to reach without hitting those milestones.  Is that just me adjusting my expectations?
What about my non-athletic limits?  I've always had a quiet confidence in my own abilities, and an inner desire to expand my repertoire.  I've never run into something that I genuinely didn't feel like I could do.  Sure, sometimes it makes sense to just have an expert do it - but it's not because I couldn't, just that I choose not to.  I could learn to change the brakes in my car - but to do it right would require a lot of training and equipment, it's just easier to hire someone.  But I could do it, if it was important to me.
And that's the crux of my dilemma, what is important to me?  I can do anything I want, but I cannot do everything that I want.  So it's time to prioritize.
I love triathlon, and I love the Ironman distance.  I'm trying to get better each season - but to what end?  Am I trying to get to Kona?  Sure, that would be nice - but it's not very realistic given my current abilities and my rate of improvement.  So I'm doing these events for fun, it's entertainment - but with a huge cost.  I spend about 15 hours a week training, though some weeks it's upwards of 20.  Add on to that time all of the recovery I do, the extra naps and the nights I can't get my laundry done because all I want to do is pass out on the couch.  And the expense of racing.  A high end bicycle is quite an investment, and requires a lot of maintenance, and you have wetsuits, running shoes, cycling shoes, clothes, arm warmers, various hats/gloves/jackets, not to mention $550 race entry fees, travel cost (you're bike's ticket costs more than yours does), and artificially inflated hotel costs in the host cities.  Plus, KT and I have spent every hour of our vacation time from work traveling to races - which has cramped our ability to visit family or go on a real vacation.
What kind of person spends a third of their income and every waking minute obsessed with a hobby?  A crazy person.  Luckily I have some incredible people in my life to help me out.  I'm not going to give up Ironman (two to do in the next six months), but I promise to keep it in perspective.  I'm crazy, but I'm not stupid - at least I don't think so :)