I'm pretty sure it is. You should try avoiding using LinearLayout and use RelativeLayouts instead.
I know weights sound attractives but I'm sure you can think about a relativeLayout workeround.
Thing is, with LinearLayout, the UI is always computed, recomputed and recomputed etc, every time you need to update something. And ppl know nested stuffs are bad for perfs. 20 is really too much, I think you can do better ;)
See this answer for more information :
Why are nested weights bad for performance? Alternatives?
Or from here :
http://developer.android.com/training/improving-layouts/optimizing-layout.html
For example, using nested instances of LinearLayout can lead to an
excessively deep view hierarchy. Furthermore, nesting several
instances of LinearLayout that use the layout_weight parameter can be
especially expensive as each child needs to be measured twice. This is
particularly important when the layout is inflated repeatedly, such as
when used in a ListView or GridView.