Getting to level 35 (180 million xp) with gen 1 with an average multi of x2 (2000/minute) = 1500 hours
Retiring 15 times and then getting to level 35 (132 million + 180 million) with an average multi of x2 (2900/minute) = 1793 hours
Because I am lazy this didn't even take into account that you only get the 1450 xp a tick when you have actually reached gen 16, which would probably add at least 300 more hours on the second outcome. Retiring to get to high level faster is not a valid argument. Also, strat battles, no one turns down a level 32, a level 28 is a lot less likely to get accepted.
I personally hated retiring and I stopped doing it as soon as I thought I had enough looms. I have been respeccing my character for 1,5 years now and I havent even once though about actually retiring it. Being low level sucks. If you enjoy retiring, sure keep doing it, if you'd rather be higher level and not bother with being crap level, stop doing it. Actually I retired my 2h alt yesterday, now I am leveling him up to shielder. I like playing a different class enough sometimes to bother with leveling. Still I always have my level 34 OP main when I want to kick ass. For me leveling alts next to a high level main is the way to go.