1. Your are not merging to master often enough. If you split your tasks and use environment flagging effectively, there's no reason why you wouldn't want to merge to master on a daily basis.
2. If you absolutely need to diverge from master so much that you have many days of work sitting on your hard drive, you should be pushing to a non-shared repository in that case, or use other form of backup.
Generally, I'm merging to master frequently (several times an hour). Things like upgrading Rails can be multi-day odysseys, however (even though there's sometimes an opportunity to make compatibility changes in master).
However, I don't see WIP branches as a problem, and certainly not one that justifies setting up additional repositories or backup systems just to avoid. If I'm working for someone else, it's not my place to set up shadow repositories all over the place, either.
1. Your are not merging to master often enough. If you split your tasks and use environment flagging effectively, there's no reason why you wouldn't want to merge to master on a daily basis.
2. If you absolutely need to diverge from master so much that you have many days of work sitting on your hard drive, you should be pushing to a non-shared repository in that case, or use other form of backup.