I know someone who is pushing 50 who just got his first jet job flying A320s for a low cost Asian carrier. He has over 3000 hours flying pistons and has around 1000 hours on a multi-turbo prop. He's not the only one either, as I've heard a few stories of pilots in their late 40's getting jet jobs, albeit with LCC's, but if you're in it for the flying and not the perks, then who cares if it's LCC that you're flying for.