$450/year sounds a bit excessive; My policy costs < $150/year for similar coverage. Before you cancel though check with your Ins Co. - I did not have TT coverage and was todl many times by my ins co that the TT was covered by my TV ins once it is hitched up (I asked this question many times).
Well....... I clipped a tree and did about $2500 damage to the awning and the siding. Talked to the Ins Co. and guess what? Even though the TT was hooked up to the TV at the time of the accident. My jaw dropped and I let the Ins Agent have - as I had asked this question many times. The good news is that the Ins Co. DID come through. I then took out separate ins for the TT.
So - check first; Not sure what you situation would be if you clipped (say) a parked car with the TT.
Good luck