Ever since I started using using Windows 8 & 8.1 I have had the problem that it takes very long time (minutes) to save larger documents in Word.
The documents are in no way complicated, they are just rather large.
If I close the document when the saving process has started it's saved rather fast (a few seconds). 
Seems to me to a bug.

Are you saving locally or to a network location or to OneDrive?

Hi,

Please try the following steps and check if it makes any difference:

1. Start Word.

2. Click File > Options > Advanced.

3. Scroll to the Save heading, untick the check box before "Allow Background saves".

4. Click OK and test the issue again.

Regards,

Steve Fan
TechNet Community Support

Sorry about the delay, but I just found that there was an answer to my question.
To untick "Allow Background saves" actually seems to solve the problem. Thanks!