I used to use them but found them to just get in the way. Not only that, the extra length on the objective can lead to more damage should you ever drop the rifle. More leverage.
Consider an ARD (anti-reflective device) instead. They're little "Honeycomb-like" devices that fit between scope and scope cap. Best of them are made by Tenebraex and sold by Europtic.
They not only cut down on glare on the lens but will also keep your quarry from being alerted due to flash from the front lens in the light.
To add, Tenebraex makes some of the best scope lens covers out there. I put a set on my NightForce and found them well worth the money. Several times more expensive than the Butler Creek "commodity" scope caps but you'll probably never have to buy another set again, as long as you own your scope, regardless of how badly you handle it.
As always, just my thoughts on the subject based on a lot of years "playing with guns"