I never have - only ever bought 3 horses - first ponies i had as a child were loans.
My first horse I still have 10 years on, shes 14 fit as a fiddle, we compete most weekends (always have) and shes never been lame in her life *touch wood*. 2nd horse, really my Mums horse atm we bought as a 10 year old hes now 16 and fine as well although showing signs of arthritus but thats to be expected with his conformation and size and isnt a worry as hes bascially a semi retired hack/nanny/schoolmaster. 3rd one we bought/semi rescued for peanuts as a 2 year old - wouldnt have been able to vet him as he was feral! He is going up for sale soon as a 5 year old and is open to the vet.