Age is less of an issue these days.
The question is always:
Can you afford to no income for 2 years +
Do you have £80k - £100k
Can you then afford to live on a salary that's probably mid-£20k's
I'd say age is less of a factor than it was a decade ago, but the T&Cs (especially the longer term earnings potential) are very different. I seem to remember people joining Air2k on £40k well over a decade ago