Yes it is pretty reliable these days. There is the odd hiccup as with anything but customer service works hard to fix those. There is a long thread with success stories.
Normally you can renew whatever plan you are already on. So if you are on an annual 500/500/500 plan you can use redpocket gold to renew that for another year
You should be able to change plans by sending a different amount of gold but I don't think that is possible from an annual plan.
You would use the app to send 99 gold using the pay redpocket option and enter the redpocket phone number in the account number field (!) Wait up to 48 hours and then it should refill your redpocket account and give you an extra year.
Redpocket advised the one person who has tried it with annual plans to do this close to your renewal time (like in the last month) to prevent complications.
Most of us are on the regular $10 a month plan so we send 10 gold to add another month. You can do this multiple times to stack months eg one of my lines is paid for up to Dec. The annual plan is just 12 months stacked all in one go but you cannot renew it monthly without changing the plan.
My Sincerest Thanks Mmfacemm !!!
That is perfectly helpful info.
I guess that since I've got around 70 gold maybe I'll swipe now & then so as to get it closer to being able to buy a renewal as you've mentioned above.
Get one of the ebay plans when they are on sale with an ebay discount. The $99.00 plan can be had for around $70.00, I refilled mine on RP using 99 gold and should be good until November 2019 if things go as expected. You could just do the 10 gold per month which was really easy to do until recently, but I'm sure that will get better in the future. But those annual plans are hard to beat even if you just pay for them.
I bought 2 of the plans during black friday sales, but ebay has 15 off 75 or 20% off sales quite often, once you are activated on a yearly plan that plan shows up as a refill option so you can use your gold for that. So yes you have to buy first and then you can refill with gold.