Coolant hoses will be good right up to the time they are not.

Hoses fail from the inside where you can't see. The inner liner deteriorates, cracks and allows coolant to migrate into the fabric reinforcement causing it ( and the bond between fabric and inner liner ) to degrade. The outer liner is just there to protect the fabric. Really old coolant hoses were a single layer with exposed fabric.

Internal hose failures tend to occur at the transition between hose and start of the barb. This is due to flexing and a build up of corrosion. External hose failures can occur at any rub point / oil leak

When I got my 97 SL320 124 K miles in 2011, I replaced all coolant hoses , bypassed the heated windshield and washer bottle. All hoses on my 97 C280 162 K miles purchased in 2014 were replaced as well.

All hoses were purchased from the evil dealer network, at pricing I'd expect to pay at any auto parts for a more common car. One hose for the SL come from Germany with a 2 - 3 day turnaround. Parts stocked in the US were a 1 - 2 day turnaround. It pays to have a good relationship with the parts dept and not storm out ranting about a $ 5 part that can be had for $ 4.99 down the street.