I want to buy clockwork grenades at the Masquerade... but here's a little problem... I intend them to be long-lasting, but... are they one-use only? will they be one-per-battle or not? Are any different?

They are single use. Meaning you use them once and they are gone forever.

It was a very good weapon, unbreakable. I guess I should have read the new stats on it :/ Sorry for your loss too, Silver.