[O] Shifting only past timestamps

[Edward Guyatt]

Hello,

I like to be reminded to check my post on Mondays and Thursdays, every week. 
When I've done it on Monday, I mark it 'DONE' so that I can stop org-mode 
reminding me until Thursday. Here's how I used to achieve this:

*** URGENT [#A] Check post                                      :important:
DEADLINE: <2015-07-27 Mon +1w -0d>
DEADLINE: <2015-07-30 Thu +1w -0d>

In org-mode 8.2.10, if I mark 'Check post' as 'DONE', both timestamps will be 
moved forward one week. This is no good, as I need to be reminded to check my 
post on Thursday.

I think I got the desired behaviour in the last version of org-mode I used, 
which I think was this 7.8.11 from this package: 
https://packages.debian.org/wheezy/org-mode

How can I make org-mode shift only the timestamps from the past?

Thanks in advance,

Ed