Feature request: Allow more granular Retry Settings intervals

[Bryan Heu]

My sass offers users a 14-day grace period to pay their past due invoice.

Unfortunately, there is no way to do this over 3 attempts using the current retry settings implementation.

The options are only 1, 3, 5,and 7 day intervals, which will never add up to 14 days and 3 attempts.

The closest I can get is 13 days over 3 attempts. It's important for me to retry 3 times.

I'd like to request the ability to add more intervals, like 2,4,6, and 8 to the interval options.

As such, I've had to re-work my sass and documentation to now say "You have a 13-day grace period", which just sounds plain silly to me...

Thanks in advance.