FortiClient licensing for occasional users

Hello, I need to buy some licenses because IPsec over TCP is unsupported and broken in the free client. We have nearly 50 users but only 18 have connected in the last week. Should I buy licenses for everyone? Can I configure EMS Cloud to automatically recycle licenses for all the occasional users? I'm trying to figure out if I should get one 25-pack or two.

Is IPsec over TCP reliable enough to replace SSL-VPN?