CC, I'll repeat for you what I told Lisa when she was having spoke problems. [No, you didn't miss it, we talked via PM.] On a normal, well-built wheel with the right specs, you shouldn't be breaking spokes in normal riding. A 250 lb guy who mashes gears could break spokes on a stock wheel, but most women shouldn't. If you've built your wheels on the hairy edge of superlightness, then it's possible. So if you've now broken two spokes, there is probably something wrong that you can find and fix. Here is what to look for:
(1) Spoke damage: I assume you've been breaking spokes on the drive side of the rear wheel, and this is the place to look. Take off the cassette and inspect the spokes for bends, knicks, and gouges. These would have been caused by dropping the chain inboard of the cassette or having some foreign object jam in there [dork disks prevent this kind of damage]. If you find spoke damage, these spokes are weak and will probably break eventually. Replace them now. If you can, inspect the 2 spokes that have already been replaced.
(2) Uneven spoke tension: The key to a strong wheel is even spoke tension. A new wheel should start with even tension, but as the wheel gets older and gets retrued over and over, it may end up with poor or uneven tension. This is especially true on a rim that is really beat up and perhaps slightly bent. If someone tries to true a somewhat bent rim, the only options are to put excessive tension on some of the spokes or to leave it less than true. The second option is better because the first option will cause spoke breakage (though replacing the rim is really best). When I worked in a shop and someone brought in a badly out-of-true rim, we would start by telling them "This rim may be bent. I can't tell until I try to true it. If it's bent, I recommend rebuilding it with a new rim. Or I can do the best I can with it, but you may start breaking spokes." If we started truing and found it bent, we would call the person to get permission to put on a new rim, or at least let them know to expect broken spokes. Today few mechanics rebuild wheels so you may not get the level of wheel service you used to. To check for even spoke tension, grab spokes in pairs and squeeze them together. Squeeze spokes all around the wheel to judge if some are much tighter than others (drive side will be much tighter than non-drive side normally, so compare on the same side). If you find one or two spokes that are very loose on a nearly-true rim or if you find a couple of extremely tight spokes, you know the rim is bent. If your mechanic returned the wheel to you this way, find a new mechanic.
(3) Hub problems are less likely, but spoke breakage right at the hub flange may indicate this.
There is nothing wrong with replacing spokes in a wheel. The wheel can be completely strong and true again with new spokes. You don't need to think about replacing the wheel because of that, but you need to know why it was breaking spokes. If the spokes were damaged, then replacing the damaged spokes will give you a perfectly strong wheel again. If spokes are breaking because of a bent rim, you need to replace the rim or the wheel (whichever is most cost-effective). If there is a problem with the hub that can't be fixed, you might as well replace the wheel.
Let us know what you find.
Oil is good, grease is better.
2007 Peter Mooney w/S&S couplers/Terry Butterfly
1993 Bridgestone MB-3/Avocet O2 Air 40W
1980 Columbus Frame with 1970 Campy parts
1954 Raleigh 3-speed/Brooks B72