How long do the MMM belts last?

[PoTreeBoy]

There's another bearing below the pulley, in the pulley support. Have you removed that? Were all the bolts tight when you disassembled it? There's a zerk in the top of the shaft, isn't there? How often have you been greasing these?

 

[MAXA]

There's another bearing below the pulley, in the pulley support. Have you removed that? Were all the bolts tight when you disassembled it? There's a zerk in the top of the shaft, isn't there? How often have you been greasing these?

This is a pic of where the shaft goes through the mower deck, to me it looks like a bearing is missing, there is one at the bottom of that hole but the top part only has a oil seal.

There is a zerk right by here,

 

[whitetiger]

You need to replace the shaft, pulley, feather key, bearings, and shaft seals.
Once the pulley gets loose on the shaft, it wears very quickly, which causes the pulley to run crooked.

 

[PoTreeBoy]

This is a pic of where the shaft goes through the mower deck, to me it looks like a bearing is missing, there is one at the bottom of that hole but the top part only has a oil seal.

There is a zerk right by here,

The bottom bearing is shot. I've kind of figured out the stackup; finally found a cross section but NOT your exact model.

The output shaft is supported by two bearings. The top one is in the gear case and is lubricated by the gear oil. There is a seal just below that bearing. Then, below the pulley, is a bearing supported by the pulley support. Above and below it are seals. It is grease lubricated; some models are apparently fitted with a drilled shaft with a zerk in the top of the shaft. I see yours is different.

It would help to have a WorkShop Manual for your model. I think Kubota recommends frequent greasing and replacing all 3 seals every 2 years. I think the gearbox seal can be replaced without opening the gearbox, but the bearing can't be. You'd be taking some risk of having to take it all apart again if you don't replace that bearing. The other bearing and seals are a no-brainer.

Edit: I see @whitetiger checked in while I was typing my tome. His input is much more valuable than mine!

 

[whitetiger]

This is a pic of where the shaft goes through the mower deck, to me it looks like a bearing is missing, there is one at the bottom of that hole but the top part only has a oil seal.

There is a zerk right by here,

The output shaft is only supported by a bearing in the bottom of the gearbox and a bearing in the bottom of the spindle housing.

 

[Toyboy]

On my deck, besides periodical greasing, blowing it clean after every use and changing gearbox oil every year, I also release the tension on the belt for winter storage.