If this was my TT, I would raise and block the trailer so there was NO weight on the tires. I would apply a liberal amount of 303 to both sides of each tire and let it soak in for 24+ hours. I would then reduce the pressure in each tire down to 10 PSI. and cover them. With the reduced air pressure and no weight on the tires, exiting crack will not expand and new cracks will not develop as the tires heat and cool with the air temp. With no weight on the tires, the tire cords will not stretch and no flat spots develop (the 10 PSI will help keep the tires round).
If I were really, really ambitious and knew the trailer would not be used for more than 6 months, I would take the mounted tires off the trailer and store them out of direct sun light in an unheated garage after the above treatment.
2015 GMC Canyon 3.6L V6 4X4 TowHaul SLE ExtCab Bronze
2016 Keystone Passport GT 2670BH
ReCurve R6 hitch, DirecLink brake controller
2005 Suzuki C50 2006 Suzuki S40