Do it for the last 6 years (English account) or 5 years (Scottish account).
I claimed, and received over £2k (once I started going overdrawn, the charges kept pushing me over - took a long time and a lot of effort to get back into the black again).
The court cases are on hold at the moment, but it's a good idea to at the very least ASK for your money back. Regardless of what the banks offer you to start off with (they told me they would offer me half as a gesture of goodwill - I replied that I wanted the whole lot back because I believed the charges to be illegal), keep asking for the whole lot back. It might take several phone calls or letters, but it's worth it.
The banks know how much you've paid in charges, but they can legally ask you to pay for a list of these charges (I think it's a maximum of £10 per account).
This site is REALLY useful when dealing with refunds from banks (and generally has lots of helpful advice):
http://www.moneysavingexpert.com
(banks specifics:
http://www.moneysavingexpert.com/reclai ... nk-charges)