svtiss,
thats why I use plug- in relays , and keep lots spares .
There is your problem. It's in the way you see things.
1 relay= around 9$
Let's say 3 spares or more=27$ +
Allready 27$ has your FET's or transistors paid for.
You need 4 x9$ =36$ + your spares, + downtime to replace your wonderful relays.
I know that if relays need to be replaced so often, that I have to stock spares, then automatically I would look for an alternative to remedy that problem, especially since you are designing a new system, and also controlling DC power.
I mostly use relays to isolate a circuit when controlling AC power(motors ect...)
Recently I have used triacs to get away from relays.
I know , that sooner or later when power, cost and apllications demand,I'll be back to the relays.
FETs will outlast any low amp relay and create very little or no noise.
Transistors are reliable and affordable. Much less then 9$ each, and could last a life time if properly setup.Add to this a couple diodes, and resistors ect...
If you have many boards to make, I would strongly suggest full electronic control for the simple fact of "reliability".
Furthermore, power consumption is minimal when you go full electronic.
Is PWM in near future???
In anycase, it's up to you.
I don't mean to minimize anything that has been suggested to you by the other members, but in the grand scheme of things, 24V----5amps---DC---, it's a moderate amount of power.
In anycase Good Luck.