Timing does have some relevance. It's no good just upping & walking if no-one has been firing on you recently. Best time is just after someone has been firing at you, wait about 10-15 seconds then saunter out of your barricade, possibly even picking up an empty pot or two on your way. No longer than this though, or it looks too suspicious, and much less and they are likely to still be aiming at your cover & take you out as soon as the first bit of you appears.
But yes, balls are very, very important for this.