I think the question you'll need to ask yourself is, "would you replace your tubulars before the next race regardless if you had previously used sealant with them?"

In all likelihood, if the dried sealant on the inside is contributing an amount to the tire's rolling resistance, then the wear of the tire's outer carcass could be offsetting it.

Personally, if it is an "A" race, I am going with fresh rubber.

I once used a tubular tire that contained sealant for three seasons (road racing and ITT). Despite presence of dry sealant from the first season, I was still able to use it during the subsequent seasons. I also topped it off with additional sealants the other seasons.

I probably should have retired it earlier, but it was eventually forcibly retired due to a freak pinch flat.

It depends on the sealant you used as to the life span in a tire. If anything I would remove the sealant out of the tubular assuming you have removable valve cores.

IMO in a closed environment, sealant stays "liquid", like in a bottle.
Like the previous poster, I kept tubular in good shape for off season by keeping them inflated, and used them for almost the full next season.
Where it's not as clear is with latex tube wich is porous, there might be some % of the sealant that would dry eventually inside the tube...
I'd keep it as a training tub but I'd use a new one for races.

Louis :-)