There's no "loop this clip" feature in Premiere Pro, but you could create a 90-second sequence with your LT in, then paste that multiple times into your main sequence.
Yeah what I'm doing so far is laying down the first title then 90 seconds later putting it down again and eventually I see the pattern in the timecode and I quickly begin to type the time code and get it done within minutes. It's not bad, but it would be nice to add a feature, where once you start to add a lower third title, especially for a long interview or speaker at an event, where you could say, "repeat title every __ seconds/minutes." Not only would this help people like me, but people doing news stories with extended interviews that require one to add the lower thirds more than once to identify the subject. Just a thought.
For now going to try it the way you suggested.
After Effects does have some scripting tools to automate some of the work you desribe here - and you can render to a movie you can import.
I would also consider creating an EDL in a text editor with that clip repeating every X frames and that could simplify process as well.