A correctly sized filter will not restrict the airflow into your engine & will save you a packet of money.
There are two things that will kill an engine at what will feel like the speed of light, & that's heat & dirt.
The air filter keeps all the fine particles out that would otherwise be abrading your rings & bores. Once the damage is done, there is only one way to fix it & that is to strip the engine & hone or re-bore, depending on how much damage is done. A quality filter is one of the best money savers you can buy.