Quote: "Is it better to delete sprites and images"
i pre-load all images i may need and never delete them.
when it comes to bullet sprites (assuming lots), i always delete them on impact but i may not delete them if they leave the screen.
assuming "a lot" of bullets as in
Liberator, initially i let the bullets leave the screen (where the map is larger than the screen) and didn't delete them until they hit something or left the map. for game balance purposes, i now delete them if they leave the screen since it was too easy to fire blindly and hit enemies that i couldn't see.
but, at some point i do always delete them while others would suggest moving them out of view, setting them invisible, etc,, and re-using them but i personally see no performance hit of note in deleting and re-creating them on demand.
liberator handles it all pretty well, even under HTML export (maintaining ~30FPS, and a solid 60 on WIN which i'm sure could do hundreds if i let it) and you see i probably have more sprites doing other things than i do bullets. ie, the tank tracks, explosions, decals, etc, all sprites (while the tanks and bullets and a few physics obstacles are all that move). speaking of tanks, i DO re-use those (immediately) where, on kill, i simply reposition them. but, again, it's just easier for me to re-use them vs recreating, adding physics back onto them, etc.
the current project i'm working on has slightly more than i've worked with before but still minimal Menu items. in trying to be efficient, i still always pre-load any images i might need then generate the sprites on demand and .insert their IDs into a MenuArray[]. when i close the menu, the last thing i do is use the array for reference and delete all sprites generated for the menu. some of that is for efficiency, the rest is simplicity in "closing" a menu.
again, others may suggest to move sprites off screen and re-use them but i think you and i are safe in deleting and re-creating where our media is relatively quite small compared to AAA releases while AppGameKit has our back in handling sprites pretty well.