inheriting vbulletin upload class?

[Acers]

I have been using the original vB_Upload_Abstract class and basically inheriting that to generate a image upload class i coded (i have added some vars i can pass to it like dest, source and dims) plus the db updates.

Now the thing is working perfectly as of now. What i am not too sure about is the comapatibility with future updates. Does vbulletin class handling change drasticaly with upgrades(i am just worried i don't keep breaking the application with every vb upgrade)

I am using common fuctions like fetch_thumbnail,fetch_imagetype_from_extension and such(basically the image handling and checking ones)

Would it be better if i leave it to this or i code a independent class to handle images and generate thumbs rather than relying on vb classes. I can do that, just tht why take the trouble if this works