That's interesting to hear Gemma. Contractors get paid monthly so their accountant would be doing something for them every month.
My clients (sole traders through to limited companies) pay me on a monthly basis. It is beneficial for both parties - the client can spread payments and the accountant knows they will get paid.
I can see your view though - especially if it means extra work for you.
Fair enough, I get your point there. But I don't use mine every month, I keep a few months worth of receipts etc and then hand them over, because we just don't turn over enough to warrant anything more, really.