My Sunbrella bimini is also 6-7 years old. I 've tried 303, Starbrite PFTE and Scotchgard. I find best results from Scotchgard Heavy Duty Water Repellent (Outdoor Fabrics) and the newer release Scotchgard Ultra Water Repellent with Mildew Block.
You should have the bimini machine washed first before applying the water repellent. Its good for 6 month. BTW, Scotchgard is alot cheaper than the other two. Unforunately for me, its getting harder to find these Scotchgard repellent in my neck of wood nowadays.
2002 Hunter 326, SV Millennium 2
1999 Macgregor 26X, SV Millennium