The research I've come across is saying that a spring or early summer marathon is not a good idea leading into triathlon season.

I generally only do triathlon events in the late summer/early fall as I find it works better for me and I enjoy it more that time of the year. I hardly ever do triathlons or swim in the ocean in the early season.

So is doing a sportive/gran forno/century ride or what ever you want to call it in the late spring or early summer good preparation for the triathlon season?