So, in this instance, I'm guessing that it be obstacle avoidance rather than runway length that would be the critical factor.
However, you can't look at the two considerations independently. In general ..
(a) a bit more flap results in a shorter roll but degraded climb
(b) a bit less flap results in a longer (often quite a bit longer due to the extra speed you are going for) roll but improved climb
with the result that
(a) on a short strip without obstacles, flap is your friend
(b) on a long strip with far away obstacles, avoid flap
(c) on a short strip with obstacles .. go by car
About 35 years since I have been in a Cherokee so the memory is a bit scratchy but I would have thought 700m should be reasonably comfortable near sea level ?
When was the last W&B for that plane ?
An important point .. all aircraft grow heavier (accumulated dirt and rubbish in the bilges and, for some private aircraft, the odd unrecorded minor mod or refurbishment here and there).
Best anecdote I can relate .. we modded a Commanche, years ago, and I was going to run the sums to adjust the 6.2/6.3. However, I had the scales in the back of the ute so we figured .. why not run it over the ramps.
Weight was out by a couple of hundred pounds .. which we eventually tracked down to a couple of radio mods and, mainly, a total interior refurbishment including a bunch of lead wool for soundproofing ...
.. logbook ... what's that ?