If we do that 30 xp is not enough at all. It would just delay what chadz didn't want , people heirlooming exponentially after they had got enough xp bonus
30xp is just the same that you get right now per generation, it would take a very long time for it to stack up into any meaningful bonus and while they're getting said bonus they're not getting heirlooms, so if they can get more heirlooms later good for them, they've missed out on a lot of them before they get to that point.
Let's face it, at gen 16 you get a bonus 450 per tick, even at double that (gen 32) you'd only get 900 extra - I believe in the past it was 10% extra exp per generation? It's been a long time, my memory is fuzzy. In which case, you're not creating the same problem since before when farming looms was a problem you had to be gen 10 to get 900exp bonus, with this you'd have to be gen 32. That's a huge difference.
Gen 10: 87million exp (roughly)
Gen 32: 278.4 exp (roughly)
Can you not see the massive difference here? Since doing one gen takes people between a week (if you're fast and play every day) and forever, gen 10 could be as quick as 10 weeks (or 2.5 months), where as gen 32 would take 32 weeks (or 8 months). Do you really think that someone is going to sacrifice 4 months (16 generations) with no heirlooms, just to get 900 extra exp instead of 450 from gen 16? It's just not going to happen - and even if it did, it's taken them 8 months to achieve what it used to take a much, much shorter time to do.
(To stop people from getting massive exp bonuses from old characters with very high generation counts due to level 15 retirements, all characters with a gen count higher than 16 should be assumed to have taken the heirloom rather than the bonus exp, to keep things level.)