I wouldn't expect particularly good temperature stability, in their normal usage, minor changes in delay are acceptable.
A caution: there are different types of chroma delay line, you mention acoustic so I assume you mean a glass type but beware that in some TVs, particularly some Asian models, an unusual decoding principle was used that used different delays. They were easy to spot because the chroma decoder used two crystals with frequencies 7.8KHz apart. There are also delays used only to delay the luminance signals by just a few uS to align it with the chroma which took longer to pass through the narrower bandwidth of its processing circuits.
Brian.