good doctrine for armored infantry?

[Volcano Man]

Yes, to add to what Rick said:

IMO, usually I wouldn't stay in travel mode unless you are on the move (in an exploit) and have no threat of enemy nearby. The trouble is, you never really know exactly what the enemy has at his disposal, and if he has the right tools available, he can exact a heavy toll on your T mode hard halftrack unit (with either airstrikes, heavy artillery, or a tank unit or two).

On the other hand, if you have a good grasp of the situation from thorough recon and you know there isn't anything in the area but rifle infantry, then sure, stay in your half tracks, but the airstrikes are still a threat.