Turn off cron and hook_cron for every module in Drupal
It is a good practice to run cron on your site. You might decide upon the frequency, keep it a high value but it is necessary to run cron to keep your site in healthy state.

If you are worried about loosing the caches when cron is run, you can install Cache Lifetime Options module and set Minimum Cache Lifetime to a very high value. This will make sure that your caches are not cleared on cron runs. Then you can Expire module for your cache invalidation strategy.

If you do not want to run all the hook_cron implementations but only a selected ones then you should consider using Elysia Cron module. It lets you run cron for selected modules at selective frequences.