I had a canthopexy 6 days ago and I'm loving the results. How long till optimum swelling goes down?

Three or more weeks for recovery then make up in my practice recommendations to my patients assuming there is a normal recovery.

Healing after eyelid surgery and canthopexyPatients vary a great deal in their recovery
rate, but usually can resume normal light activity or work 3–4 days after
surgery, using dark glasses and make-up to camouflage the swelling and
discoloration. The patient will usually be presentable without dark glasses in
10 days. A small amount of residual swelling persists for many weeks, but
gradually disappears.you should be safe to wear lashes 3-6 weeks after surgeryt

This is partially dependent on how your own tissues are doing.  For that reason, you should ask your surgeon this questions because he or she will know how you are healing and can provide individualized guidance on this.

I'm glad you are enjoying the results. Swelling usually resolves within a month and is usually safe to apply extensions. Ask your surgeon during your follow up visit what his recommendations are. Good luck.

Thank you for sharing your case.  Usually, the swelling will completely subside by 2-3 weeks after surgery.  You should ask your surgeon when they feel comfortable with you wearing mascara and getting eyelash extensions.  Good luck!