It is important to remember that the process called leveling must be properly performed by means of a leveling screw that needs to be fixed to the foot or flange of the motor, or even through very thin sheets of compensation. After the leveling process, the height difference between the engine mounting base and the engine per se can not exceed 0.1 mm. In case a metal base is used to adjust the height of the motor shaft tip with the driven shaft axis tip, it should be leveled on the concrete base.

https://www.mrosupply.com/tensioners-and-idlers/154408_fa3502_fenner-drives/

If it is the alignment between the motor and the driven machine, it should be considered one of the factors that contribute most to a significantly longer life, thus prolonging the engine life. The misalignment caused between the couplings can cause high loads which are widely capable of reducing the bearing life, causing vibrations and, in very extreme cases, even causing the shaft to rupture. The leveling of the electric motor must be performed so that it is possible to correct any deviations of flatness that may exist from other processes and accommodation of the materials.