Hi! Just as was said by PraiseLuka and Haibara Ai, it is most beneficial to save. Seal scrolls do not depreciate in price as time goes by, so saving will not ever really lead to a negative outcome. On the other hand, using seal scrolls too early or without rebate wont give you any additional benefit. Always look for other beneficial opportunities for everything you do. Rebates are always great and worth waiting for!

~Jib