Hi Simeon - It would be normal to use Alumina Ceramic inserts in these heavy wear zones. So you should expect at least 1 year of use before needing to replace these parts. Contact Salter Cyclones.

Simeon, is this for planning or an actual situation? Do you have any ball-chips in your grinding circuit?

It is recommended that pressure drops, whenever possible, be designed in the 40 to 70 kPa (5 to 10 psi) range to minimize energy requirements as well as reduce wear rates.

It has been found that a pipe size which produces a line velocity of 200 to 300cm/sec (7 to 10 ft/sec) is high enough to prevent particles from settling, even in horizontal sections, but low enough to minimize wear.

When properly designed the central chamber becomes a mixing area and the line velocity should be lowered to approximately 60 to 90 cm/sec (2 to 3 ft/sec). This will help insure that each cyclone is fed with the same slurry concentration as well as the same particle size distribution and also will reduce wear rates.

It is typical that the high mass particles or coarser particles tend to pass the first cyclones and report to the final cyclone. This results in the last cyclone receiving a higher feed concentration of coarser particles, which accelerates the wear of the last cyclone as well as produces a coarser separation due to the higher feed density.

Cyclone Construction varies greatly from one manufacturer to another, but the majority of the designs includes metal housings with replaceable liners with replaceable liners with the most suitable liner material varying from one application to another. It is also common to utilize several different lining materials within the same cyclone to optimize wear characteristics.

Natural gum rubber is the most common material utilized due to its relatively low cost, excellent wear, ease of handling, and it is not fragile. Applications where gum rubber is not suitable are those where the temperatures exceed 60C or there are large amounts of hydrocarbons present in the slurry such as oil or other detrimental chemicals. Ceramic materials have found acceptance as cyclone liners for the apex orifice as well as other areas which exhibit severe abrasion. These include areas such as the lower cone liner and vortex finder. Nihard has also proven to be an acceptable wear material, especially for vortex finders and other areas which require strength as well as abrasion resistance. Other elastomer materials such as neoprene and nitrite are also utilized when hydrocarbons are present or when the temperature exceeds 60 deg C. Urethane has found acceptance, especially in areas where the solids are relatively fine.

See This and That and https://www.911metallurgist.com/blog/hydrocyclone-design-equations-and-sizing-parameters-calculations/sizing-and-selection-of-hydrocyclones

With good ceramic, a life > 3-4 months should be easy.
Krebs/FLSmith also has good cyclone wear materials.

This link here could interest you: Cyclone with in-situ replaceable liner system and method for accomplishing same 

Interesting and useful comments. Something to take into consideration specially with high pressure cyclones and coarse material is the underflow launder lining, which finally could shutdown the circuit to have the liner changed with ceramic or a harder material than original rubber.