I worked my way up to Light Null quickly. I sat at that until about level 400. Then I went to Light Thetacron.

Now, level 630, I'm half-way upgraded to Light Quasi-Chaotic.

The issue isn't if you want the attack bonus or not. It is if you can afford the maintenance or not.

i've had hvy null for quite some time and i plan to sit at that till i can afford hvy theta's ( which won't be too long) and im 340, i will then sit at theta till im 700+ ( tbh i dont want them at all im happy with my nulls and will probably just up my hull and other things instead)

The best time to upgrade is when you can afford it and able to pay for the upkeep

QFT

Don't bother upgrading past heavy nulls, after that they're too expensive for too little gain. I hit heavy nulls eons ago and stopped there. At rank 288 I just don't pull enough high quality minerals to pay the upkeeps. Since I had all mods except scanners equipped on my ship by heavy star destroyer, I stopped adding decks and now I'm working on crew, specifically tac officers. They more than compensate for only running nulls.

I say this because. With my current upkeep of 15billion/day (with discount) I am able to make the upkeep plus the cost of invading a planet everyday. Of course you need x 16 mining planets to be able to do this.

As remric says, it all depends on your mining levels and whether you can afford it. I don't know many people at my level who do not have at least heavy theta or mostly thereof, and for the most part people have quasi's. It is a question of being able to afford it, because yes after null's the price tag for maintenance gets fairly hefty. But if you can have the mining to support it, why not?

Of course, you might have to choose your poison so to speak. Some people want the best cloaking and spend the credits on cloaking + scan, but it is all up to you. At some point you do have to pick and choose what your ship is going to excel at.

The higher level weapons might be more show then anything, but every little bit helps. If you want to further your mining, I highly recommend myrthar for awhile as a race to help yourself eventually get those higher end mining planets. Once you have that, you can eventually switch your race, but until then it never hurts to maximize as much as possible.