Here are some tips to help you maintain them:
Cleaning: First off, you need to clean your eyelashes daily with a compatible cleanser. Make sure to use a lash shampoo that is oil-free.
Brushing: Combing your dry lashes will prevent them from tangling and avoiding clumps.
Curling: In general, it's best not to curl your lashes when you have extensions. If you absolutely must, you can use a heated curler (never a mechanical one).
Keep off the eyes: It's best to avoid rubbing or scrubbing your eyes harshly as it can cause extensions to shed early.
Refill: Getting a refill every two to three weeks allows you to reduce the cost of doing repeated full sets and also maintains a beautiful lash line.
Hairdryer: To dry your lashes, never use the hairdryer on the hot setting and always go for the cool setting. That being said, you could also let them air dry on their own.
Avoid oils: These are notorious for degrading the lash adhesive and causing poor retention. You need to be careful of which cosmetics you use around the eyes.
No salts: Swimming in the ocean requires extra care and some preventive measures if you want your extensions to remain beautiful.
Sleeping etiquettes: It's aways best to sleep on the back with extensions. You should also replace your cotton pillow covers with a soft fabric like silk or satin to reduce friction on your lashes.