Even in the 1850 most of the cabinet was against expansion to the Amur and Pacific and this was a local initiative in which success justified violation of the explicit orders.
As most of us know, the Russian Empire did end up expanding at Chinese expense, in 1858-1860, gaining the lands of the Amur District and maritime province, while the Qing Dynasty was reeling from the 2nd Opium War and the Taiping Rebellion (and other rebellions). As the Russians conquered the Kazakh hordes and Turkestan, they also seized corners of Qing Xinjiang a bit later as well.
But apparently, up until it happened, most of the Russian cabinet was quite timid about it.
How long could this forbearance have feasibly lasted? Could the Russian Empire have conceivably reached the turn of the 20th century with its southeastern frontier at Asia a the Pacific being at a Stanovoy mountain range, where it had been set by the Treaty of. Nerchinsk about 200 years before?
What could have been the consequences?
If it were somehow possible, and Russia has neither Vladivostok, nor Khabarovsk, I imagine it would not have much of modern Pacific battle fleet to speak of at the end of the 19th century, nor would I imagine a 'Triple Intervention' occurring against Japan's Treaty of Shimonoseki terms imposed on Japan. I believe that intervention was spurred by Franco-German competition for Russian favor, but a Russia that hasn't seized the maritime province isn't one that is gunning for Port Arthur.
Would a lack of Russian annexations in outer Manchuria have prolonged Qing Dynasty/Manchu resistance to mass Han Chinese migration to Manchuria, or Manchuria north of Liaoning? A trickle of settlers had always gotten through, and state capacity for enforcing exclusion was declining anyway, but I think Russian encroachment had something to do with relaxation of entry of Han migrants into the region.