Not an expert, but it seems practical to bring over enough each year to reduce your total tax paid to zero each year, then save the rest for future years. Certainly moving extra over that amount would be a waste. Up to that point moving it over amounts to an instant 'gain' of whatever the marginal tax rate you would have been might be - which would compound fairly quickly.
It also depends how old you are. At 71(?) you need to convert all RRSPs into an RRIF and start taking income from them (and paying taxes on that income). So if you are 40 that's not a big deal and the payoff will be worthwhile. If you are 65 it is a different story. It might still be worth it, but it is different.
You might also consider moving some of that money into a TFSA, which will then be tax sheltered forever - income and withdrawals.