Yeah I have a friend who does that to his mana too ..but with no cover ..its faded big time now....but if you have a white or silver reflecting boardcover it shouldn't get too hot ..but un zip it as it might act as a oven bag .I think it's more the direct sunlight that will age it .i guess with a new board your are always a bit worried ..after a year ..you get a little more relaxed .which size glide did you get ? I have the 11' glide Great flat water board also smashes through waves ,without hardly budging .
i guess the winter sun isn't as hot .unless your right up north .maybe get a reflection sheet to put over it too.

if it means getting a sup in the avo ..I would take it ..just check it through the day ,make sure it doesn't get to hot .
if its cooking leave it at home ,if its just warm ,should be ok .
if its over 30 c I wouldn't be leaving any sup on the roof for more than 1-2 hours .if I can help it .
i don't think the GS models, like the Glide .have the final lamination coat like the GT .( Matt finish) .so maybe they will handle more heat .
quote me if I'm wrong .

ask JB.