When one places one or more Pokémon in Gyms, a "Defender Bonus" becomes available via a shield in the upper right corner in the shop screen. The couple of times that I've put Pokémon into gyms, I have later on clicked on the shield and received some items (quantities of stardust and gold, if I recall correctly), and the shield then shows a countdown timer until the next bonus is available (I believe - haven't actually had any Pokémons in Gyms long enough to find out). The bonus doesn't just automatically happen, one needs to trigger it by clicking on the shield.
Does anyone know of some especially good strategy for when to claim the rewards? Is it better to wait until many Pokémons are assigned to different gyms? Does taking the bonus after placing your first one keep you from accruing bonuses for subsequent Pokémons placed in gyms until the original timer runs out? Does the amount of bonus vary depending on when you claim it, or is it fixed for the number of Pokémon one currently has in Gyms? (Or somewhat random, but not influenced by timing?) Is there any association to calendar days, or is it strictly a countdown timer? (i.e. If the time is currently close to midnight, is there any particular reason to hurry to accept the bonus before, or to delay until after, midnight?). Thanks!