suffix "less" or prefix "re"

[areev]

When do we pronounce suffix "less" (les/lis) or prefix "re" (re/ri)?

ex. "stainless" I like to say (steinlis)
"careless" I like to say (keirles)

is there any rule?

Thanks.............

 

[albertino]

When do we pronounce suffix "less" (les/lis) or prefix "re" (re/ri)?

ex. "stainless" I like to say (steinlis)
"careless" I like to say (keirles)

is there any rule?

Thanks.............

(Not a teacher)
To me, stainless is pronounced as -les, and so is careless, while re is ri:.

 

[Raymott]

For me ‘less’ is always /ləs/.
‘Re’ is always /ri:/ or /ri/, depending on whether /ri/ is stressed, as in ‘re-read’, or not, as in ‘redeem, research’, etc.