Spaghetti Squash - Learning

Today I made a pasta dish for dinner but I didn't eat the pasta.  I instead made a spaghetti squash.  I've done this before as a substitute and it has been just fine.  I learned, however, that even a spaghetti squash can go bad.  I had had it for almost 3 weeks.  It still looked fine, wasn't squishy or anything.  But after I cooked it and started shredding it, the consistency was a little thick and not quite as soft.  Then I tasted it and it was horribly bitter.  So it was either bad to begin with or 3 weeks is just too long to have it on hand.  My advice would be to use it within a week after buying.