A "move over" offer

We're planning to embark on a cruise in about a week's time.     This will be our first ocean cruising experience, so it will be a bit of a change for us since we're normally (but not always) "independent" travellers. 

But with just over a week to go, an email  arrived from the cruise line, including the statement, "Princess is extending a special offer to guests booked on the March 16, 2014 Dawn Princess sailing. Move to any alternative sailing (up 14-days) and receive...." (basically) a refund of the whole fare (credited as refundable onboard credits) plus an upgrade.


I had done quite a lot of reserach on the internet about various aspects of ocean cruising, but this was new to me.  However, when I searched some cruising forums for the expression "Move over offer", I found that such offers are not uncommon, and occur because cruise lines - like airlines - deliberately overbook cruises and sometimes they don't get quite as many cancellations as they plan for.  In fact there are some cruisers out there who relish the opporunity that such an offer provides.   To receive one on our first cruise would be regarded by some as indeed fortunate.  There is a theory that if you live in the departure port, you're more likely to receive an offer. 

The idea of receiving back the entire fare (presumably not the taxes, though) as spending money on a future cruise - with it being refundable if you don't spend it - seemed too good to be true.  But, yes, according to the on-line forums, this sort of offer is indeed sometimes made!    Pity that the notice given to us was so short and that the alternative dates for the cruise we want to do just wouldn't work for us.