Little problem with multi-licence renewal

Last year I had 4 machines running NIS. One on a single licence, and three on a three machine licence.

PC 1 on a single licence expiring now and

PC's 2, 3 & 4 on a three licence pack expiring mid November.

Earlier this year I scrapped PC4!

 

Now, I have a new three licence pack ready to do the renewal with. My question is - can I use the three pack on the two remaining three pack machines PLUS the one that was running on a single licence? i.e. PC's 1 2 & 3 on the new three licence pack.

Obviously, I have to renew PC1 now, so can/should I renew the other 2 now so that they all stay in sync?

 

My apologies for the convoluted problem. I hope you can understand me.