I don't know where you're getting 4 hours from... With a 15 minute break it only takes 2 hours and 35 minutes to take a PT. I'd say just do 1 per week with an excellent BR and you shouldn't find it too strenuous.
I bought a $9.99 watch from CVS. Ya know, a little painter's or masking tape placed just-so can transform a $9.99 watch into a 35 minute-ish or 180-ish watch.