Buy from a company that checks them before they go out. The more high quality models should all come collimated and stay that way unless you whack them hard. Whilst you can “collimate” them yourself, this will only be true for your eyes and your eye spacing, making them possibly less collimated for others. To FULLY collimate bins requires a specialist rig, don’t worry there are people in the UK who can repair/clean and recollimate bins. The costs are reasonable, but probably not cost effective for the cheapest models. Look at Binocular sky’s reviews for good quality models and treat them well and you’ve nothing to worry about.
Peter