question time for a novice

I am looking at buying ARG as a longterm investment for 50% of my share portfolio.

However ARG has over 10 years moved in tune with the XJO albeit slightly above. Neverthelss mirroring the trend.

For a longterm investor;

1. What is the incentive to hold these shares considering they have conceeded 20% of the SP since its high ?

2. Appears to be in a consistent longterm downtrend ?

3. Is there a "right" time to buy, ie considering dividend payments etc ?

4. Is margin lending a consideration due to stability ?

Would appreciate a bit of guidance with the above.

All the best.