a) This top-up offer was good until May 1st. So maybe 2-3 months or so. But I have to say that every offer has it’s own terms. They may not all be like this one. Like rebates they expire and have rules.
b) Yes I have the original GM card which I understand is no longer available. I have had the card for many years and have saved thousands on a number of GM cars. The original card was better in that you could accrue $500/year. After 7 years the rebate points start to fall off the end every month.
I’m not an expert on the new card but I believe I saw something where you could get 5% credit up to $250/year and then 2% rebate after that. Go to their website or Google it. I’m sure the CC community has all the fine details.
These rebate cards though have high(er) interest rates. So if you plan to carry a monthly balance then they are no bargain. They are best for those that pay em’ off every month.