What to do about my Cisco router several years old before a disaster/failure?

My cisco 1760 is just for passthrough and has our DNS servers coded in.   The t1(full 24 channels data line) is plugged into it an then feeds my wg box where I set up al my rules and my DMZ.  This router is over six years old I'm guessing and there are no signs of issues, but...  I am concerned about what to do before this router gives out. Should I be?   I have 35 users in my FL office and 2 in WI.  The vpn ipsec tunnel is established using the wg boxes, as well as the DMZ configured and plugged into the wg hardware.  

Is ther a recommendation for the next simplest cisco router that can replace this one and the advantages?  Is it possible to utilize one of the inherited hw listed below as a backup?  Would replacing it with one them actually be in improvement in performance, etc?


The specs on this router are:
Cisco IOS:  Version 12.2(15)T8
The IOS is upgradeable.  
DRAM:  64Meg (expandable to 128Meg)
FLASH:  32Meg (expandable to 64Meg)

I also have some HW that I inherited when we moved into our new office:
-10baseT/100baseT 24 port Catalyst 2900 Series Cisco 1eth and 1 DC input             
-2600 Series Router Cisco2620  2 DSU/CSU WIC 1eth 1 console 1 aux port            
-2600 Series Router Cisco2610  1 T1 DSU/CSU WIC                        
-1720 Router      Cisco1720   1 T1 DSU WIC 10/100 eth console and aux port      
-VPN 3000 Concentrator      Cisco  CVPN3005                        
-VOIP Gateway with 8FXS ports and SIP Support MP-108a/FXS/AC/SIP (qty 2)

Thanks!