Each item of information in your CR has its own date of running, and also its own degree of impact on your credit score.
So a lot depends on what is deleted, or is being requested to delete through GW letters..
To clarify this, take a typical account example.
You have an OC account that goes 30 day late, then 60 days late, then 90 days late.
You could then have a charge off, and/or a collection posted.
So on one debt, you have, in this example, a possible five separate items of information posted to your CR to deal with, each of which is hurting your score.
30-day lates are minor derogs in credit scoring, so not the first thing to worry about. 60+ lates with the OC score more in FICO
COs and CAs are major derogs. Definately a major impact on your score.
As has been said, payment of any bad debt never, in and of itself, removes the prior reporting of the delinquency.
Your option at that point is to ask for GW deletion. Your highest benefit targets for GW are the more significant derogs.
The problem you face in asking for GW deletion is that the granting of a GW deletion by one who previously reported it is, in affect, asking them to violate the credit reporting rules they have agreed to. The credit reporting manual for all CRAs specifically states that prior reporting should NOT be deleted based on subsequent payment of the debt.
If they abide strictly by this practice, and tell you so over and over they cant or wont delete, being a "squeaky wheel" will probably see your GW letters just wind up in their trash can,with no response. I am not suggesting that you shouldint be persistent, but they have no obligation to even respond, and your annoyance might not be of any significant squeak to them.