You asked for it, and now you've got it ...
Now, instead of trying to calculate how many spin credits you might use ahead of time, you may now simply purchase an unlimited monthly subscription and use Spinbot all day, without limit. You may purchase a single month subscription, or go for more time (6 months or a year ahead of time) for significant cost savings when compared to the month-to-month rate.
If you still have "old" spin credits, then you will still be able to use them until they are all gone. You may also purchase "new" spin credits, but these new credits cannot be used through the front of the site, or through the browser-based website.
So, if you want to use Spinbot through a browser from this point forward (if you have run out of the "old" spin credits), you must purchase an unlimited monthly subscription through your account management page. If you want to purchase spins credits to use in your own website or app (only if you're a developer with your own app or website), then you must purchase the new Spin credits (see link at the bottom of your account management page). The cost of these new spin credits is the same as the old ones.
If you are not a developer needing spin credits for your own custom app or website, then don't bother thinking about it.
If you have spin credits leftover from before this change, then you may use these credits as before until they are gone. If, for some reason, you decide to purchase an unlimited monthly subscription while you still have "old" spin credits, then your old spin credit balance will not decrease as long as you are rewriting content through the front of the website (through a web browser). If you use the credits through your own app or website, then the credits will decrease as usual.
Developers: If you have old spin credits leftover then things still haven't changed from the point of view of your API-consuming app. If you have old credits and then you purchase new credits in addition, then then the old credits will be consumed first, then the new credits. From this point forward, whenever you purchase credits, they will be counted as the "new" type of credit that cannot be used through a browser, or from the front of the website.
So now, if you are using the website to rewrite your content, then there's nothing holding you back. The time is now to create all the valuable content that you possibly can.