Colt! It was nice to read, how the beginning is going.

TwitchyFish, with the useful tips of the others (Stavros, Sam) you will improve quickly, I'm sure. The experience is, that you can go relatively easy to about 4 minutes with your PB. Then it is a bit harder to improve it.
Back to Colt's advice: now sometimes when we train static, I just say 'Can we start with 3 min?' and then go!

And we do it. So you can reach this level with a lot of training - the point for you is to see, that these times are not beyond human limit. It is onlz the matter of practice, but it is very important, that there are days, when you are weaker (usual cause is not enough sleep, when you are tired, when you are ill, not drinking enough (water!

, dehydratation I mean), and in these times you cannot do as much as normally. You have to accept this, and not trying to do more! It is important. You have to understand the signs of your body, and behave according to them! This skill is rather mental, but it is very important in this sport, since you stay under the water, which is a dangerous environment for the human beings, so you must be responsible (to yourself).
have a nice time while training, and beat your PBs,
Jee