How do I know if I need a new bottom end?

About to install my new Cylinder Works kit (cylinder/piston) along with a new cam chain. The shop I go to were advising me (/selling?) to replace my connecting rod in case the bottom end blows and then needing a whole new cylinder. How likely is this scenario? Nothing blew in my motor and my current cylinder is fine. My piston was definitely done, I just got the whole cylinder kit because the price difference vs just getting a piston was negligible. I'm 95% sure it's the OEM bottom end for my 2005 WR450F, but I hear no noise in the bottom end when riding and when pulling up/down, I couldn't feel any play in the connecting rod (cylinder is currently off). Is there a sure-fire way of knowing when new complete bottom end parts are needed? How often should one completely rebuild a bottom end? How do I know if I need a new bottom end (besides having a catastrophic engine failing)? Should I replace anything "just in case"?

What are the logical steps to follow? Play in the connecting rod=new bearings crankshaft bearings only? A new connecting rod only? A whole crankshaft assembly? Hot Rods bottom end rebuild kit? I've never touched the bottom end on an engine before, so this is all new territory for me. Apologies if my questions appear stupid.

I have the feeling that a simple top-end rebuild is fine and all that's needed as WRs seems to be quite good longevity-wise... Might be a classic case of shops trying to sell extra stuff (ex: ~$175 for a connecting rod here, vs something like $80 on rockymountain!)

Any insight appreciated.

Edited by Bitteeinbit

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