I do a lot of gravel road riding but have only had to replace my belt once in 8 years. That was after going over freshly laid chip and tar which was still hot so the tar stuck the stones to the tires and made them fly everywhere......
Same here; while I don't really do the 'hard arse' miles that some do (& more power to them too!

) or ever actively avoid ryding on the dirt (hell, it can be so much fun that I've even been know to go
looking for dirt & gravel to ryde on!! :clap: ) from the mileage/ryding info that many people post up here, it seems to me that I've likely done more miles
OFF the sealed stuff than many Spyders have ever done
ON the sealed stuff, only I don't have the extra/missing belt guard...

. But I do check my belt & sprockets fairly regularly for stones/damage, and while I haven't had to replace a belt on my 2013 Spyder (
yet! 
) I hafta agree, it's the 'still sticky' recently laid chip seal stuff that's the worst for getting into things & sticking/creating issues if you don't keep clearing it off/out! :gaah:
There's lotsa machines out there running belts like ours that get ridden on & off the dirt with few if any belt issues, so ryding on reasonable unsealed roads with a little care, ie. 'normal' dirt/gravel roads, shouldn't ever be
too much of an issue on your Spyder, while loose gravel marbles or sand over a firmer layer can even be a
real blast!!

hyea:
At the risk of repeating myself, when it comes to ryding your Spyder on dirt roads, don't be
scared of it cos you think the belt will melt/shred if it gets any dust on it, they really are pretty robust things; and with a little care, you should comfortably
be able to
Ride More, Worry Less! - Only
do check your belt & sprockets for any embedded stones when you next have an opportunity/get home from that ryde! :thumbup: