A lot depends on where in Europe. Some places simply do not negotiate very well with individuals, even to their disadvantage. Others do. Always worth a call to a sales manager during business hours. Depending on your needs, you may also be able to negotiate for the inclusion of services you might need or the exclusion of things you do not need.

1. Points and other status benefits cost hard cash to the property. Consider negotiating those away.
2. Housekeeping. Do you really need it daily along with turndown service?
3. On the other hand, might the property include some amount of laundry?
4. Some F&B credit?

Also consider local taxes. In some jurisdictions, longer stays are not taxed or are taxed at lower rates.