Note that half-lives are not the only thing to consider. Half-lives are just an average of how long it takes for half of the original drug to be out of a person's system. A half-life not necessarily the same thing as duration of effects, some drugs have active metabolites with much longer half-lives than the original drug, and everyone'e metabolism is different. Some effects, such as respiratory depression, can last longer than the noticeable or therapeutic effects (like decrease in anxiety, muscle relaxant, anti-convulsant, "high", etc).
So I'm assuming what you mean is would taking a long-lasting benzo or other CNS depressant pose a danger when taking an opioid 24 hours later? It really varies depending on the benzo (or other drug) taken, the dose, the dose of the opioid you're going to be taking, your metabolism, how long you've taken the benzo or other drug, possibly which opioid you take, and (especially) your tolerance to both benzos (or Flexeril) and opioids. As for the drugs you mentioned:
Clonazepam has a duration of effects of around 12 hrs and a half-life of 18-50 hours, and diazepam (Valium) has a duration of effects of around 6-8 hrs and it's main active metabolite has a half-life of 36-200 hours, so I would be concerned about taking an opioid the day after these. If you are going to do this, first start with a much lower dose of the opioid than usual, since you have no idea how much of an effect the benzo will have on it.
Cyclobenzaprine (Flexeril) is not a benzo, it's a weird drug and we don't really understand how it works yet, so it's possible that it could have more adverse effects with opioids than just CNS depression. It also builds up, reaching a steady state after 3-4 days with levels 4 times higher than if you only take it once. The half-life for a single dose is 8-37 hrs. Duration of effects seems to vary a lot. Again, I would be concerned about taking an opioid the day after. If you are going to do this, first start with a much lower dose of the opioid than usual, since you have no idea how much of an effect the cyclobenzaprine will have on it.
TLDR: Yes, they might interact with opioids even a day later, so if you're going to take opioids I would take less than usual.