There was not much and some misleading information on this so here is my opinion on the direct bus connection from Pokhara to Delhi.
It took 30 hours and there was no flat tyre or anything of the like. We started at noon in Pokhara near zero kilometer bus stand but taxi drivers seem to know 'Delhi bus stand'. We took an AC bus which is 4000 NRP for foreigners (directly booked at the 'modern era' ticket office). The first two seats on the left side were fine as they offer more space for your legs. We crossed the border at Bhimdatta in the West the next morning (but they said they sometimes take another border the same day in the south). The ride is long and roads are as you can imagine not the best, but time passes faster than you think and they stop at restaurants with
good and cheap food.
Just consider that alternatively you would first need to drive to Kathmandu for 7-8 hours and probably catch a flight just the day after.
I would do it this way again.