Do age spots usually get worse with each subsequent IPL treatment in the long run?

Thank you for your question eps207. I understand your concern.
IPL is a great treatment for facial rejuvenation. Sometimes the dark spots get darker before they get lighter. This can take 2 weeks or more. Prolonger discoloration can be treated with creams. For my patients I recommend an initial series of 6 monthly treatments. Results are seen slowly over time. Patience is important. Please consult with a doctor for specific recommendations. Good luck!

Thanks for your question, eps207. You should not be getting MORE hyperpigmentation from IPL treatments, it should be the opposite. IPL is not a permanent solution because you will continue to go about your daily life after treatment and with that, your skin will continue to age. However, if you are diligent about wearing broad-spectrum sunscreen everyday, reapplying every 2 hours when out in the sun & taking steps to protect your face from direct exposure (wearing a hat, sitting under an umbrella, etc.) then you should be able to enjoy your results for several years after the procedure. 
I'm not certain that I understand exactly what you're saying about your post-treatment routine, but I can tell you what I recommend for my IPL patients: 
-Sunscreen (SPF 30 or higher) for 2 weeks both before AND after treatment
-Avoidance of sun exposure if at all possible for 2 weeks both before AND after treatment
-If sun exposure is unavoidable, wear sunscreen & a hat
Although IPL is not technically a "laser" treatment, it carries with it some high risks and over the years I have seen many patients who have had bad results when it was performed by the wrong hands. Make sure you are seeing a board-certified dermatologist who has experience with laser & light-based treatments. Ask to see some of their before & after pictures! 
I hope this helps!