To check the bolts, you only option is to take them out and look at them. The lower A-arm bolts on strut rod eliminator units like Trees' are the most critical and should be checked at least semi-annually. The rest of them are relatively lightly loaded. If you have strut-rods, all the rest of the bolts are probably not over stressed.
The rest of the system needs to be checked for corrosion and cracks. The former is pretty straight forward.
If you have strut rods, the strut rod mounting point on the frame is the critical point. I don't know how many rods I have seen at rod runs that have these mounts cracked and usually not even hanging on the frame. If it is welded to the frame, check that weld. Preferably the bracket is welded and gusseted to a 1/4" or 3/8" plate or 1/4"x4"x4" angle iron and bolted to the frame. Check the body of the X-member around the lower A-arm bolts for cracks also.
Front ends with strut-rod eliminators are living on borrowed time, IMHO. All of the aftermarket X-members I have seen are not robust enough to withstand fatigue stress so will eventually crack. This is totally different from tensile stress. Tensile strength is the resistsnce to being pulled apart by a single load application. Fatigue strength is much more subtle and a lot lower value than tensile strength. In fatigue stress failure, a part is stressed to a level far below ultimate tensile stress thousands or millions of times (could be vibration or just normal service - pot holes, joints in the highway, etc.). Even though none of the individual loads can possibly fail the part by itself, the accumulation of the loads initiates a crack at a stress riser (sharp inside corner, hole, nick in the metal, etc.). Heidt's economy X-member is the worst example I have see. It has right-angle joints in the plates that make up the body of the unit that are in the highest stressed place they could be. Check very carefully around the entire bottom bolt hole area for the first sign of cracks or bending.
Th rest of the system should be ok, just check for problems.