upgrading old PCs (RAM... overclock or not)?

We upgraded CPUs of several servers/workstations and are thinking of RAM.  
I'll give standard & overclock megahertz and ask advice.  Numbers in 
parentheses aren't in guidebooks, just newer 'memory support' documents so 
don't know they're overclocks or merely faster RAM at slower speeds, and 
first of these doesn't mention overclocking at all in guidebook but newer 
'memory support' document mentions faster RAM.

* ASUS Sabretooth 990FX: DDR3 1033MHz to 1866 (or overclock 2000?)
* ASUS P9X79 LE: DDR3 1066 to 1866 or overclock 2133 to 2400 (or 3000?)
* GigaByte GA-Z170XP-SLI: DDR4 2133 or overclock 2400 to 3466
* BioStar X470GTA: DDR4 1866 to 2667 or overclock 2933 to 3200 (or 4600?)

The ASUS use much slower RAM (faster was expensive then) so should I 
upgrade to fastest standard speed or might slow-to-medium overclock not 
take a year off system-/logic-/main-/mother-boards' remaining lifetime?

If we don't put Sabertooth 990FX in garage to run, it might be retired 
(storage/spare or give to PC shop) later this or early next year, but I 
still want it faster remaining months/year.

I thought about overclocking P9X79 LE to 2400+ and GA-Z170XP-SLI to 3466 
but guess for more hardware lifetime that's inadvisable rather than 
fastest standard speed or slow-to-medium overclock?

The GigaByte is already on only/fastest standard speed and will probably 
be used several more years though soon become a family spare PC (also 
number-cruncher for BOINC ( http://boinc.berkeley.edu ) and/or 
cryptocurrency mining, which these all do when unused such as at night).  
GigaByte was no help advising on overclocking Z170XP-SLI nor Z270-HD3P I 
almost replaced with recently, just cautioning might cause problems/
instability (damage?).

I overclocked X470GTA to DDR4 3200MHz but mentioned after almost three 
years a capacitor (beside RAM) popped off, so should I decrease to 
2667MHz?  It was my main PC and if/when repaired/replaced (similar/same 
system-board) will become family main PC... already thinking of upgrading 
(can't find adequate system-board) but don't want it to pop again in a few 
years due to overclock.

Even Sabretooth 990FX is fast enough if someone just wants to edit one or 
two documents, or email, or browse maybe one website, and number-crunching 
until wears out, so what users want all four workstations for (so-called 
'use case') is hardware lifetime, not overclocking unless won't 
significantly shorten that, but nice if can overclock without 
significantly shortening that, for faster number-crunching... Sabretooth 
990FX had five-year warranty but we still use it a little 12 years later.

Of course if/when new Ryzen 9s and i9s or better are out, hopefully for 
full-to-extended ATX/SSI-CEB system-boards with one or two plain PCI slots 
(micro-ATX is inadequate for those plus large display/video/graphics card) 
I might ask whether worth overclocking DDR5 SDRAM on any those or might 
end up same situation (as X470GTA) after a few years it pops again.

Some people who know a lot about hardware said overclocking RAM certainly 
makes system-boards wear out faster, but that capacitors may wear out 
around same time anyway... unsure what that means... maybe if not well-
cooled, or system-boards may wear out by time one wants to upgrade, or 
other parts not as fast but can't be replaced like capacitors can?

I asked a local electronics repair shop and searched online capacitor 
shops for days but couldn't find anything I thought would be a good 
replacement.  Details are the following.

    5K238
    C270 (C has dot so don't know it's really C or another symbol)
    16V

I saw similar listed but might not either fit or last long, and repair 
shop didn't reply if can get replacement, and after a couple weeks, 
BioStar hadn't replied about getting just capacitor (and since warranty 
page was hard to find and after buying one must register within a month--
about shipping time--my non-expired warranty is invalid).