Your question doesn't ask about the fate of your security deposit, if any. That's normally what triggers these disputes, and there's a very elaborate set of provisions under the Texas Property Code about when and under what circumstances, and with what notice, tenants are entitled to get back their security deposits. Those provisions also have time-tables.
To answer your question definitively and with confidence, any Texas lawyer would need to review your lease. Lease documents quite often include provisions regarding the extent of the tenant's responsibility for damages.
In general, absent provisions in the lease to the contrary, a tenant is responsible to pay for repairs for damages he's caused that exceed "normal wear and tear. That's an obligation that arises either directly from your lease agreement or by implication from the contractual landlord-tenant relationship, so -- unlike the security deposit return issue -- it's governed by the general Texas statute of limitations for contract-related cases, which is four years.
You may be able to make some other use of the landlord's delay. You say "not knowing what the damages are." In any lawsuit, each side is entitled to get from the other, before trial, evidence that relates to either side's claims or defenses. So you would be able to compel the landlord to show you what evidence it has to prove that (a) there were damages (and that they were beyond "normal wear and tear") and (b) that the damages were inflicted during your lease term (rather than, for example, by a later tenant). If the landlord doesn't have credible evidence to show both what happened AND WHEN, you can use the landlord's delay to argue that his claims aren't credible (believable).
But as far as you having a magic bullet that will just cause the judge to say, "Seven months? No way! Get out of court, landlord!" -- No, there's not anything like that, unless it would be in a very unusual provision of your lease. (And most leases are written on forms drafted by lawyers for landlords, so the likelihood that the lease would contain any requirement that the landlord's claims be brought in less than seven months is pretty small.)