why not go in clean using this as an opportunity to practice flap failure
The occasional landing with zero flaps, for the flap failure practice is appropriate when runway dimensions permit, but flapless landings as a matter of course, in a single Cessna is a less than great idea. The flaps are there to be used, and make landings slower and safer. Their use greatly reduces the chance of a tailstrike or porpoising. Anything you do in a 172 with flaps up is probably happening at least 10 kts faster than it would be with flaps 40 (or 30 for later models). If there is "an event" at landing, with flaps up, it's going to be much worse than were the flaps to be down, and someone might to ask why that happened.
Though 40 flap climbouts are not approved for the 172, they can be safely accomplished, if the departure space is available. This capability is required by the certification requirement for "balked landing", which in the case of the 172, assures a rate of climb at gross weight, with 40 flaps, of at least 200 feet per minute (at sea level, standard atmosphere). I'm not advocating this be done, as there are a lot of certification requirements which should not be done in general flying, but they have been demonstrated at certification, to assure that margin of safety.
For some reason, some pilots seem reluctant to regularly use 40 flaps in a Cessna. I wonder why.....