The Optimus V definitely should not be behaving like that. With proper care (as with any phone), the OpV is a smooth running little phone and does not require a task killer. Are you sure you don't have an app(s) misbehaving and causing issues? Have you tried performing a factory reset on the phone? Sometimes this will fix a lot of issues (replacing files and/or apps that may have become corrupt for whatever reasons).
Id try some troubleshooting steps to rule out other things that may be causing the issue:
Uninstall all apps that did not come with the phone.
Make sure all default apps are up to date.
Try rebooting the phone.
If none of that works then perform a factory reset so you will have freshly installed system files.
If you try all of the steps above and nothing works, then I would get the phone replaced. The warranty is good for one year from the original date of purchase.. as long as you are the original owner and have not rooted the phone.