Severing the feeling would only be, well, temporary though, which would be useful in the short term, but it wouldn't do much in the long-term especially if she can't spam it. Asuna & Javen also don't necessarily need to go all out the entire time either, so they can save energy for the long run like cobalt could in hyperspace (Though again, it's unlikely she can escape it to it with the movement speed disadvantage and time magic, so this might not be a reliable strategy especially once Asuven know what it is).
Javen in particular would be really good at this considering he can exert himself for a week straight. Asuna doesn't really have any long-term feats so far, but she does have an extreme degree of supernatural willpower, and even when she gives a fight 1,000,000% she's not really tired afterwards. Plus in [Playback], she's in the 4th dimension, so she can have a couple dozens seconds to take a breather if she absolutely has to.
Asuna can support javens motivation with social influencing too to keep him going if need be, which also helps.
Javen could also definitely use his imagination manifestation to make a super potent energy drink or something to keep him & asuna going too, which will be a massive help as well especially in the long run where all 3 combatants need to stay awake, So this would be another option for that alongside supernatural willpower