How to enable KeepAlive in putty command line
You could connect as per your post and then right click on the title bar and "Change Settings", "Connection", and put in a number in the "Seconds between keepalives" (I usually put in 60).
If needed, you can apply this change to all sessions by default by saving over the "Default Settings" session before connecting.
It depends on what causes connection drop. It's not putty itself, so it's either endpoint server, or some NAT on the way.
If that's NAT, switch on
Enable TCP keepalives on Connection category, as described there: Using KeepAlive in PuTTY | Nth Design
If it's endpoint server that drops the connection, then the only reasonable way I can think of is using
screen, so you'll be able to reattach terminal if connection dropped suddenly.
How to access attached screen after connection dropped | magp.ie Blog