This is exactly how they are supposed to work. I am an ASE certified tech, worked for Toyota for a while, and now work for Honda. It is as they say a design in the transmission so as to warm the fluids before it will shift. Also if you have ever noticed when you drive it in the morning if you were to floor it the transmission will not allow it to go to the rev limit, rather it shifts it early. I have a 1995 Camry with 170000 miles on it, and it does this exact thing. Make sure you have a good quality Toyota fluid in there, and it is clean, and other than that you are good to go my friend. I hope this helps somewhat...and that you didn't spend to much on that transmission.

Brendan