Varied questions: mines, sats, experience

[Taera]

So the question finaly formed in my brain:
What is the practical use of mines in large-scale games against human players?
Very well. in the earlier game it gives the advantage to the defender.
A little later, even with LCs loaded with Mine Sweepers II can take out minefields relatively easy, given the 100 mines-per-sector limitatioin.
Are the mines any effective?

Sats.
Same situation as with mines - early on some advantage but then it ends.
In my Last game (against the AI, the first realy serious) i've noticed that large sats with appropiate weaponry are rather expensive and it does take the same time to build 6 sats and to outfit a BattleStation of the latest tech.

So, someone please explain me why should one bother to build 20 sats when he can build 3 battlestations of much greater stopping power?

Now the Last question: experience.
Is it me, or experience gives ships a big advantage over the untrained fleets?
OK, this is realistic. But still.
In my game i was battling Sergetti - a race with enchanced speed(+1) and engines one level ahead of me, and defensiveness(+20), plus their berzerkers culture (+10) for a grand total of +2 over my speed and +30 to all defensive rolls.
Early on their ships had their edge - my ships were missing to the most even with better sensors (sensors II against ECM I). So i massed my forces over a planet with fleet & ship training facilities (i thought it'd be a good time spending untill all the fleet is built and arrives etc). Later when the fleet was massed (LCs armed to teeth with Mesons) i encountered their early mines and spent time building my own mine sweepers.
Then there was the retrofitting to the new engines and weapons (my technology-rich race made it realy quick to reach PPB 5 and higher enginess).

The result was 17 ships, each ship having +20 to their skill and +20 to fleet skill.
Then there were the battles.
My fleet have _never_ _been_ _hit_.
Never. No hit. I exterminated the whole many of their ships - four massive (20+) fleets with the smallest ships being cruisers and biggest battleships (a few, the High Tech of the race).
So my fleet was unscathed.

Now it is approximally 30 turns later.
The fleet is elite +29 and each ship is either elite of +28 or legendary closing to +40 (the flagship).

I've encountered several other races. The fleet exterminated a grand total of 30 dreadnoughts from the Drushocka, and again - no losses. The sergetti are literally dead. And all above was the result of early training.

Is the training is realy so effective? If yes it realy but realy justifies the early research of military lvl2.

OK, long post with a lot of personal info. But hey, this is my first sucessful game!