Please tell me what CALs I need to do mstsc of WinServer

I have recently purchased windows server and now wants to purchase some user CALs. Few users will do mstsc of WinServer from within the premises and few customers will do the mstsc from remote location, a different city. Remote user will login via internet connection into the LAN and then do mstsc of WinServer. 

Please tell me exactly what products has to be purchased to facilitate this. I have zeroed in on the below:

1. WinSvrCAL 2012 SNGL OLP NL UsrCAL

2. WinRmtDsktpSrvcsCAL 2012 SNGL OLP NL UsrCAL

If this is correct, then please guide on how exactly this works? For example, The user doing mstsc from within premises requires item 1 only and users doing mstsc 
from different city requires item 2 only, or both 1 and 2 is required in both case.

The terminal server services gives a countdown of 120 days from date of installation and ultimately expires and all connections thru mstsc stops. And then the server is reinstalled. So one major concern is whether purchase of these CALs will stop this inconvinience for ever?

Please reply asap. CAL requirement is very urgent but can not proceed unless this clarity comes from you.