Cleaning sand, dirt, dust and other debris after every swing can help extend the life of your golf clubs. It's also important to keep your clubs protected and never hit from any area or surface that could cause damage. If you're looking to purchase a new set of irons, it's best to buy from a reputable online retailer like Nearly New Golf Clubs, who have a huge selection of over 800+ clubs in stock.
Harder cast irons are much more robust than other types of golf clubs and can last longer. If you're satisfied with the performance of your existing irons and maintain them well, checking that the grooves are good and making sure that the club face has no obvious damage, your irons should last a long time.
Finally, if your game has improved significantly, it may be worth considering if your old clubs are still the best fit for your new improved game.