I might stay for a period of 1-4 months in the Westin Rotterdam. The location is fine for me and I have not found an appropriate rental apartment so I consider the Westin a great choice if they are willing to give me a reasonable rate. The lenght of the stay will depend on how fast I find an apartment.
I want to contact the hotel directly to negotiate a rate.

How to start ? Call, send an e-mail ?
I could also stop by at the hotel and negotiate on-site. Should I make an appointment with the manager ?

I want to stay during the week only. Is it clever to ask for 5 days a week or should I say I need the room for e.g. 30 (or 60) days ?
I would prefer to stay Mon-Fri and check in each week, maybe they have a place to store some personal belongings that can stay in Rotterdam over the weekend!

What arguments will the hotel manager use, how could and should I contradict ?

Am I correct that you only get starpoints for stays shorter than 31 days, i.e. stays of 30 days or less earn points, therefore I would love to check in each week ?
How about upgrade chances if checking in each week ?
Can one earn starpoints on special rates offered by a hotel ?
Can the hotel give away VIP status for a long term customer ? Is it likely to do so ?

Probably my SPG Platinum status will help, should I call the hotline ?
Or even use Amex Centurion service for a first contact establishment with the Westin property in Rotterdam ?