Better for the RV to keep it covered but not necessarily for your pocket book. If you pay $300 a month to store it somewhere for 6 months out of the year that $1800 is money that could be used for the additional maintenance costs incurred with exposure to the sun and elements. Same applies to the cost of a cover and anything other than a Sunbrella fabric is not likely to last more than one season, though whatever you get if it is blue/green/yellow it will last a lot longer than one that is brown/gray/black over time as more UV light is getting reflected.
If you only need to visit the RV once a month while in storage then you can look for a cheaper location that is further out of town.
These concerns are part of the reason we did not get a large MH or 5th-wheel that we could not park at the house. We also knew that if it was at the house we could take more spur of the moment trips throughout the year.
