I have been to St. Petersburg 3 times now and I am still looking forward to my fourth trip. It is an amazing city.
The "shopping" thing is an issue. Some love to shop some dont. PLUS the guides are very "regimented" as is pointed out above. I had to almost force our Red October guide to make some time for us at the vendors last trip.
They make a lot of profit on their stores so I do understand why they insist on stopping at the Red OCtober store. It is the same as having to go to a Turkish Rug store in Turkey.
Next trip I may have a van do a "shopping afternoon" and another van do something else. It is hard to know what to cut out though.