When is it a good idea to change your lawyer?

The law firm we have been working with so far doesn't seem to have a lot of experience in working with other startups. It also seems like they require more time for solving our legal issues than we think might be necessary. Of course, since I'm not a lawyer, I'm not 100% sure what's the norm. So, when should we generally consider switching our lawyer regarding how time-consuming/costly that might be? Thanks!