I am noticing on some popular torrents that I have finished and continue seeding, that tixati is connecting to up to 10 other seeds.

The Peers list is full of "Both Peers Complete" entries. Is this an issue to be concerned over? or just the way it has to work?

I think it is normal. Tixati gets IP list from DHT or a tracker and tries to connect to peers. It works the same when transfer is 100% complete except Tixati disconnects other seeders promptly. Basically you are seeing this because those transfers are popular, with lots of other seeds.

It doesn't have to be this way, Tixati could just announce DHT/tracker and then sit and wait for connections, however this would be slower. For example if you just started Tixati and tracker TTL is 30 minutes, some downloaders may wait up to 30 minutes to get your IP address.

Another more important reason is: when behind NAT or firewall you are basically "unconnectable". Obviously you wouldn't be able to seed at all, when waiting for connections only. I guess there are lots of people who can't set NAT and firewall to allow incoming connections to Tixati and automatic solutions (UPNP NAT-PMP) may be insufficient (firewall) or not working at all (not enabled in NAT).