* Long-term copper price forecast up 8.2 pct at $6,948/T * China demand seen supporting outlook for prices * Rising labour, energy costs add cost inflation By Harpreet Bhal LONDON, Oct 7 (Reuters) - Long-term copper prices should be boosted by rising cost inflation and a bullish outlook for demand from top consumer China, prompting analysts to revise prices for the next 10 years up by more than 8 percent, a Reuters survey showed on Monday. The average long-term cash copper price is forecast to rise to $6,948 a tonne, from a previous Reuters estimate of $6,420 a tonne, a survey of 11 analysts conducted over the last three weeks said. Long-term price forecasts, of 10 years plus, are used by analysts to evaluate what they call the "fair value" of a metal, which helps miners to determine the feasibility and potential profitability of future projects. These prices tend to be conservative as investors will not commit to a project that only makes money if prices are high. Highlighting the difference between long term and current prices, benchmark London Metal Exchange three-month copper was last trading at $7,207.00 per tonne. "We find that the cost base has moved sharply higher and marginal cost producers will struggle to survive with prices much below $6,500 a tonne," Standard Chartered analysts said. "This supports our view that even if demand weakens, there is limited scope for copper prices to fall." Boosting optimism about the outlook for demand from China was renewed confidence that the country has put a floor under a protracted slowdown in its economy. To boost activity, its government has accelerated copper-intensive infrastructure spending, sustained spending in public housing and cut taxes for small firms. China makes up about 40 percent of global refined copper demand. Rising costs for mining projects is also a factor underpinning the outlook for higher prices, including rising labour and energy costs and declining ore grades. "While not a component of costs per se, declining head grades contribute to cost inflation due to larger volumes of material moved and greater processing requirements," BMO analysts said in a note. ALUMINIUM, NICKEL PRESSURED Of the six base metals, only aluminium and nickel saw downward revisions to their long-term price forecasts on growing oversupply concerns. Aluminium price estimates were slashed by 8.2 percent to $2,225 a tonne, while nickel forecasts were down 1 percent at $19,500 a tonne. Stocks of aluminium in LME warehouses hit record highs around 5.5 million tonnes in July, but vast amounts of the metal are stuck in warehouse bottlenecks and bank financing deals that keep the metal away from consumers. Nickel, a key component in stainless steel, has been pressured by a ramp-up in new supplies and dwindling demand, making it the worst performer so far this year among the six base metals on the London Metal Exchange. Analysts expect tin prices to rise nearly 6 percent to $21,150 due to a deficit market, while long-term lead prices are seen up 4.5 percent at $2,312.50 and zinc forecasts are up 1.3 percent at $2,202.30. (Editing by Veronica Brown and James Jukwey)

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