Austria Hungary was probably done politically by November 1914. Germany was running out of rubber for gas masks and this alone might have prevented the war from continuing into 1919. But assuming that the Germans played the west front better in 1918, delayed the allied counter offensive and stripped enough allied forces out of Italy, Salonika and Palestine to prevent counter offensives on those front the war could have continued until 1919.
This would have been historically interesting:
1) A major Allied offensive in 1919, with a major american effort, backed with a major increase in tanks and planes, and more forward thinking strategy on how to use them.
2) A major strategic air offensive by the allies
3) More effective mine barrages and the complete defeat of the u-boats.
4) The victory would be largely considered an "american victory" with ramifications at the final peace.
5) The east would be under german occupation for at least 6 more months with butterflies on how the russian civil war plays out.
However the central powers still loses. The Germans OTL always overestimated their military position so probably will never be able to find away to agree to any terms with the Allies until the Allies have reached the Rhine and its a complete surrender situation.
IMO the best chance for a better peace was between Amiens and Salonika in the August 10 - September 15th time period. Many (Most?) Germans leaders knew the game was up, The Austrians were begging the Germans to ask for a peace conference. Perhaps if Ludendorf was dismissed after Amiens this could have happened.
Potential September 1st cease fire agreement:
Germans evacuate France, Belgium, Alsace-Lorraine within 30 days, without demolitions or looting. German warships currently in Flanders or Austria to be surrendered, all other German warships go to Baltic sea.
Austrians evacuate Italy back to 1914 boundries, ports of Trieste, Pola and Cattaro to be surrendered to a radius of 30 miles, Entire Austrian fleet to be surrendered. Albania and Serbian Macedonia to be evacuated.
Turks surrender in Medina and Aden, Germans surrender in east Africa.
Otherwise lines remain as they are, Germans and Turks to not push further in the east.
All allied POWs to be returned within 60 days, All German enlisted POWS to be returned in 120 days (German NCOs and officers to be kept as POWs).
Peace conference with all parties present to begin in 30 days in Amsterdam.
This peace ceeds certain military advantages to the Allies, but the Central Powers still have powers of military resistance to be able to negotiate.