flintlock frustrations!

[Mr. 16 gauge]

O.K. guys....I've been shooting traditional black powder for several years now, but I am somewhat new to flintlocks. I bought a Cabela's trade musket about a year and a half ago, and due to work restraints and other factors, I haven't been able to get out and shoot it as often as I like.
One of the things I notice is that I don't get many 'sparks' out of a flint....seems I get 6-8 good ignitions, then nothing! Not even the "flash in the pan". I am using both english and amber flints, with roughly the same success. Should I be cleaning my flint and frizzen off after each firing? Not really sure why I am not getting a decent shower of sparks.

Anybody got any insights? Thanks in advance.