Currently I play with Dyson Spheres off, because they like to eventually group up and not go anywhere. I have just seen too many bugs with them for now.
So assuming no Dyson sphere, I can offer some random scouting advice. My typical scouting pattern goes like this.
1. Send all Mk I scouts on auto-scout. Eventually these reach planets with tachyon beams.
2. Send all Mk I scouts on a specific path, to scout farther.
3. Send all Mk I scouts in a transport which I send off past the tachyon planet, and then go to step 1 or 2 depending on what I see.
This gets my quite a lot of scouting coverage quickly, especially if I stay on top of my scouts, sending them away when they are built. Depending on your economy and how quickly you take planets, transports can be hard to come by, since they are expensive just to send on scouting.
I can't mention any drawbacks to maximizing scouting coverage. Sometimes its even nice, because it aggros a few ships from AI planets (ever-so-slightly slowing down their buildup).
Guard Posts, at least in the latest Beta, don't have tachyon beams. I wonder if they still do in the latest official (you mentioned detection by a Guard Post)
Hi Panopticon! Hope you have fun playing this game. I've worked my way up to Diff 9, but I'm having trouble right now. Sooo much replay value in this game. I keep coming back. Find a friend to play with, it makes it soooo much better! Especially if you can have voice chat.