Guest list question & RSVP Question

Who's doing an A & B List? How did you determine who went on the B list? Since we only have space for 100 (Dad said I could go over but not by much maybe by 10?)

Problem is everyone on my A list is someone really important to me, I already made the hard calls, like people I haven't seen or heard from in years or some work people etc.

Second question is regarding RSVP date, if I am going to work from a B list, then how far in advance should I send the invites out to the A list to give me time to send to B list people as A list people decline?

This is what I am thinking:

Send A List out March 1, with RSVP date of March 31st

Send B list as A list declines?

My thing is it will look rude to the B list people because I won't be giving them enough time to RSVP? or should I send out a bit later like Mid March and but the first week of april as an RSVP?

If you have less than 20 on your B-list I would send them all out together. If you have more than 20, then I would send out the A list invites in Mid February with the RSVP March 31 so you'll can send out B list as the A list declines and still give them enough time to RSVP.
I hope this makes sense.

We have an A & B also
A is all the people that we Have to and Really want to have 125 -

B list is everyone that we would like to have and it would be nice but arent going to loose any sleep over it

I am sending out my first round out 10 weeks before with rsvp date at the 6 week mark so that we can do the 2nd out 6 weeks before -