Just a "wild" idea or thoughts instead of dealing with multiple visa fees, lines for border crossing & long train rides - I know of friends that've done extended stay at the Harbour Plaza Resort City at Tin Shui Wai in (Yuen Long area) N.T. - it's a short 3 to 5 minutes walk to the MTR Light Rail Ginza Station, that will connect to the West Rail & main lines going everywhere in H.K. Depending on your travel dates - there are ongoing specials - quoted online rates for late May averaged $145 USD per night including service charges (no taxes or surcharges, as you know) for the deluxe room at 400 sq.ft. with a sofa, mini-dining & kitchenette.

http://www.harbour-plaza.com/resortc...dations-en.htm

There are photos & reviews on tripadvisors . com about the property to read about.

"Commute" time should be a little bit shorter but at least you will not need to do daily border crossing. HPRC, from what I understand, isn't in the same tier as the Marriott - but it seemed well managed, comfortable & spacious by H.K. standard. Rates for H.K. hotels keep going up each year as mainlanders continue to "flood" it and shop until they drop - our accountant's family just visited and their packaged (air & hotel) nightly rates were $350 USD+ for an older & remodeled property on Nathan Road in TST, go figure

The last time we visited post Shanghai Expo, we took the midday MTR/KCR rail toward Lo Wu with the intention of crossing over to Shenzhen for a quick lunch & tour, and it was still crowded and got off at Sheung Shui - not so sure if it's going to fun and/or worth doing it over 2 weeks, YMMV.