Sounds like there'* something wrong. In my '01 SSEi, once it is up to full temp, the TC locks up right away... No waiting. If anything, I think that the TC should unlock more often for me. I tend to get a little bit of shudder going up small to moderate slops between 40mph and 50mph.
Now until the temp goes above 160* (I believe, but correct me if I'm wrong), the TC will not lock up at all to run higher rpms to get the engine warmed up faster. If you know someone with an Autotap or other similar scanner, get it scanned while driving down the road. An Autotap can see all of the TCC settings (what the comp is requesting as well as (i think) what is being given). That would be a good place to start.