Assign more than one Service port to a VIP?

It really depends on what you are doing. Setting up a VIP to do standard HTTP (port 80) and HTTPS (port 443) doing two virtual hosts is less overhead on the F5/LTM. LTM will block all ports execpt 80/443. If setup a single virtual host to do all ports, then had an iRule, the iRule will cause more overhead.

Now if you were doing something that was using lots of ports, then a single virtual host on multiple ports with an iRule maybe less overhead than having a bunch of virtual hosts.