i replaced my brakes a while back, right after my rear brakes wouldnt work, so i blead the hell out of the brakes, they were good for a while, but now they get a little spongy once and a while, do i need to bleed em some more, or could it be something else

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Trent
---Car---
89 Firebird
305 L03 TBI A4
t-tops

---Stero---
Pioneer DEH-P730 Premium
Infinity 2way 4652 4x6's
Pioneer 4way ts-a6985 6x9's
profile cl640 110x4
2 pioneer 12" ts-w303c subs (selling if anyone wants em email me)

Future:im profile 1200sx 900watt x 1, and a pioneer cdx-p1270 12 disk cd changer