Can someone please help me understand the current situation
regarding SIMMS?

I have a IIsi which I will probably keep for another 2 years.

I would like to add more memory, ie go from 5 MB to 17 MB.

I know that I will need 4 x 4MB, 80ns or faster SIMMS.

Which SIMMS, 30 pin or 72 pin?
Would the SIMMS I get today be usable in 2 years with a 
newer, more powerful system?

Any insight would be appreciated.

Thanks.

Rob