I am gonna be replacing tires, and repack bearings, adjust inspect brakes, etc.

This would be a real Pain in the a$$ having to do one axle at a time. Not looking to make a bunch of trips to the tire shop.

Ive never attempted this, but was thinking maybe 2 bottle jacks, placing one in front of the front axle on the frame, and another behind the rear axle on the frame. Get it up and set it on jackstands, then lift the other side same way and set that on jack stands. I have heavy duty stands and stuff, just don't wanna be bending the trailer up. Boat and trailer weigh 12000lbs together. C Channel Myco triple axle with leaf springs. .

That is the way I've done it. I have a box frame trailer and it doesn't seem to creak much. I wouldn't worry much but I go back and forth between the two jacks to keep the weight somewhat distributed...

With the tongue jack down I used one bottle jack on each side between the axles and just pumped the jacks up a little on each side till it was the height I wanted. Than I put 4 jack stands under the trailer, one on each side in front of the axles, and each side rear of the axles. When I was done the trailer was supported by 4 jack stands and the tongue jack.

the way i do it is i lower the front of the trailer as far as it goes,,i put 2 jack stands at the back of the trailer ans lift the top so its tight on the trailer then i lift the tongue with the forklift just until the tires are off the ground and set the front on jack stands..

or just jack the trailer between the tires with the jack on the Triangular Equalizer high enough and set the jackstands on the front and rear axle..

This works well.

You can also just raise the tongue stand as high as possible and use a heavy duty floor jack on the trailer frame behind the rear axle. I have a 3-ton floor jack I bought used for my dually and it does this task perfectly.

ive used a three ton jack lift up the axle and set it on blocks, work your way around.

I took the chicken way and put the boat in the water and attacked the trailer bearings, seals, and brakes with the unloaded trailer.

Get 2 20 inch or so 6x6 and cut it into a wedge leaving like 8 inches of flat to pull / back up onto. That way you can do both the fronts at one time and then both the rears at one time. Keep one of the wedges in the bed for when you get a flat on the road. It saves time and effort. Works good.

And with the front on the truck you don't have to worry about it going anywhere.

I'll disagree here. IMHO, you are putting too much weight on a single axle, even for just a maintenance window.