The extender - when compressed with one hand - should be at a length that the head of your penis almost is in front of the extender. In other words, the compressed extender should be a bit shorter than your stretched flaccid. In that way, the extender can be worn more comfortably with the noose tightening downwards instead of beeing like «a hangman» for the head. You can be able to not having to tightening the noose so tight, allowing for some blood flow to the head, and also jelq some fresh blood forward to the head every 20 minutes, and by so, doing longer sets. 2-2,5 hours before a break, and maybe more hours per day if you have the time. You don’t mention at what level of traction you are extending. Some years ago, the springs in an extender usually maxed out at 1500 grams/a pair, now they are selling extenders with 2800 grams springs or higher. I would say that - go with the old school, do max 1200-1500 grams of traction. Some guys recommend to go even at 900 grams for higher numbers of hours per day. It is time under traction that counts, and lower traction than 2000+, is more comfortable,and will usually not have problems with extender slipping off, giving you the possibility to wear it for up to 12 hours per day, as the producer recommends for higher gain rate.
Too bad you haven’t got any gains yet, but give it time, and use heat like the other guys says. An IR lamp, or simply a rice sock heated in a microwave. Do some neewbie routine is also a good idea. Good luck.