Uptime:

"This wormhole has not yet begun its natural cycle of decay and should last at least another day." means 24+ hours
"This wormhole is beginning to decay, and probably won't last another day." means under 24 hours
"This wormhole is reaching the end of its natural lifetime." less than 4 hours, not verified.
"This wormhole is on the verge of dissipating into the ether." -- not sure the timer
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Mass:

"This wormhole has not yet had its stability significantly disrupted by ships passing through it."
More then 1/2 - Approx. 500,000,000 kg

"This wormhole has had its stability reduced by ships passing through it, but not to a critical degree yet."
Less then 1/2 but more then 1/10th
Approx. 500,000,000 kg to 100,000,000 kg

"This wormhole has had its stability critically disrupted by the mass of numerous ships passing through and is on the verge of collapse."
Less than 0.1 of the total