While the parts guys at Toyota may not "recommend" changing the 6 heater hoses with the Ts, I'd still do it. On the three vehicles where I've changed these, two of them had hoses that were "less than optimal." If the Ts are old enough / bad enough to be an issue, (a) you also have to be concerned about losing parts of the crumbling Ts down into the heater system, (b) you gotta figure the hoses can't be great after that much time, and (c) since two of the heater hoses are connected directly to the heater core, it's better to cut those off rather than tugging them / twisting them and risk damaging your heater core (causing a leak.)
It's a little extra money (around $100 for 6 hoses and 2 Ts), but I think it's worth it........Just my $0.02
good info!