When we started to seriously look at buying to retire we saw it as a ten year plan, which is what it worked out to, and our view is that the ten years soon passed. Although during that time we did buy a bigger villa for retirement, and then eventually after two years sold the original villa.
If I was starting again would I buy in advance and use for holidays, possibly not in use terms. Long term rental for first part of retirement, and then take time to decide whether you like it, where you like best and what you like best is an attractive option. However, part of me thinks that there are bargains to be had - particularly at the end of the season - both new and especially re-sales, combined with what I think over the next ten years plus will see Fethiye (and indeed Turkey) become a more established and desirable place for holiday/retirement home (including a growing number of Turks looking to retire or work here) that the investment in a property bargain - stress again best at end of season - could be a very viable long term plan.
What ever you do, good luck. If it is any guide we are enjoying it here.