By intermediate do you mean between the stuffing box and the gearbox ?
On my boat I have a steel roller bearing with grease nipple in a carrier which is bolted to the hull, its called a 'Plummer block bearing' and is located between the gearbox flange and the stuffing box.
The shaft passes through the stuffing box (which I replaced with a PSS seal), located immediately behind the stuffing box is a short 3'' cutlass bearing.
Where the shaft exits on the outside of the hull a standard 6'' cutlass bearing is fitted.
These bearings are fitted to stop any 'whip' in the shaft.
What is extremely critical for long life and smooth running is the condition of the engine mountings and the engine shaft alignment in both the vertical and horizontal planes.
This is measured at the gearbox and prop shaft flange coupling and must not exceed 2 thou in either the vertical or horizontal planes even if you have a flexible coupling fitted.
To adjust undo the nut on top of the engine mounting, below the engine mounting arm is another nut which is used to raise/lower the engine.
To move the engine sideways use a large crowbar/prybar before retightening all nuts, then check again for accuracy.
The only maintenance required is a squirt of grease in the plummer block bearing until the grease starts to show around the bearing, turn the shaft 1 or 2 turns by hand, add another squirt or two, wipe the outside of the bearing free of any grease once a year.
I bought my boat second hand which had vibration through lack of maintenance and alignment of the engine/shaft by the PO and
it helped to get the price down.
I replaced all the engine mounts and bearings and the difference in noise/vibration was amazing, its actually not that expensive if you do it yourself.
I've since covered some 3,000 miles around the European canals and the Mediterranean and everything's still as good as new.
As I said initial alignment is critical and maintenance is very simple.
If you read my blog on here called 'Windmills and Wine' there are photo's and descriptions of the engine mounts, new cutlass bearings and PSS seal.
p.s. You can't buy a half size bearing, standard cutlass bearings are usually 6'' long so buy 2, precisely cut one exactly and put one half in along with your boat spares should you ever need one for the future.