Recommendations for RV cover

I have tried RV covers and my issues are they let the water and dirt through and the trailer is messy when you take it off. I haven't found one that lasted more than 3 years. So for the past 5 years or so, I have bought a large tarp ( 30 x 20 ) and cover it with that. You can't just fasten it with the grommets alone. I bought 2 or 3" strapping and go completely over the top and under neath. Then use grommets to keep it stable.I pay about $60 each for the tarps and get a year or 2 out of each one. A lot cheaper than trailer covers and your rig looks cleaner in the spring.