In the older GalCiv2 I used to wait with the development of advanced weapons until the first couple of enemy warships used to fly around and I would know what they were deploying. I would then choose my research accordingly to counter their weapons.
In GalCiv3 so far I found that to be less of a necessity due to early weapon tech being useful longer, but it can still work out in the long run. If one is quick enough grabbing some ressources (not difficult), they shouldn't limit your possibilities anyway.
However - I'm still quite new to GalCiv3, so take that advice with a grain of salt.